Science 8R Mechanical Systems Review PDF

Science 8R Mechanical Systems 2022-2023 Name: Answer Key HR: _____ 1 Science 8R 2 Science 8R 2022 Assessment and Assignment Sheet for Science 8 Mechanical Systems: Dates:September 26th to November 7th, 2022 What do we want stud...

Science 8R Mechanical Systems 2022-2023 Name: Answer Key HR: _____ 1 Science 8R 2 Science 8R 2022 Assessment and Assignment Sheet for Science 8 Mechanical Systems: Dates:September 26th to November 7th, 2022 What do we want students to learn? (Essential Learning Outcomes) Analyzing machines (function, design, simple machine components, fluid systems components) Evaluate machine modification on mechanical advantage, gear ratios, work, and efficiency Sources of energy for mechanical devices (potential and kinetic energy) Lab skills Calculate mechanical advantage, gear ratios, work, and efficiency Analyzing machines (function, design, simple machine components, fluid systems components) Evaluate machine modification on mechanical advantage, gear ratios, work, and efficiency Sources of energy for mechanical devices (potential and kinetic energy) Lab skills Test dates and project deadlines Project or Test (Assessment of Learning) Date (subject to change) Topic 1 Quiz Tuesday, October 11, 2022 Topic 2 Quiz Thursday, October 27, 2022 Design Portfolio (Catapult) Monday, October 31, 2022 Written Final Exam Friday, November 4, 2022 Unit Exam (MC) Monday, November 7, 2022 Homework and Practice Assessments for learning Resources September 26 - October 10th: Engineering process, Booklet pages 6 to 25, technology development over time, mechanical devices, Section 1 review assignment, force and speed advantages, gears, hydraulics and Section 1 review Quizizz pneumatics. October 12 - October 26th: Mechanical advantage (real & Booklet pages 26 to 50, theoretical), energy, work, efficiency Section 2 review assignment, Section 2 review Quizizz October 28th - November 7th: Unit Review and Unit Final Unit review assignment, (written and multiple choice) Project Assignment Sheet and exemplar Project : work days throughout unit 3 Science 8R Key Terms/Concepts Quiz #1 Quiz #2 Function Mechanical Advantage (MA) Design Theoretical Mechanical Advantage (TMA) Criteria Energy Constraint Potential Energy Mechanical Device Kinetic Energy Simple Machine Gravitational Potential Energy Complex Machine Law of Conservation of Energy Subsystem Energy transfer Component Energy Transformation Screw Energy Convertor Inclined plane Work lever Work input pulley Work output wedge Efficiency wheel and axle High efficiency fixed pulley Low efficiency movable pulley Friction block and tackle pulley class 1, 2, 3 levers speed advantage force advantage effort force load force gear train driver gear follower gear idler gear gear ratio multiplying gears reducing gears parallel gears gear chain Pascal’s Law pressure hydraulics pneumatics Areas where cross curricular connections might be made: Mathematics→ calculation and graphing of work, efficiency and mechanical advantage. Social studies→ history of simple and complex machines. Construction→ building and constructing a rubber band car. 4  Science 8R Engineering Design Process – Notes Define the problem Identify function (purpose or job) of device Criteria (what device must do) Constraints (real world limitations (materials, cost, time to develop, etc.) Plan solutions Brainstorm ideas Choose one design (how a device is put together) Make a design drawing Make a Model Build a prototype (early example of technology) to test design. Test the Model Test the prototype repeatedly, making qualitative and quantitative observations Reflect and Redesign Evaluate the design - Did it meet the criteria? What were the strengths and challenges? How will you improve the next design? Practice: Identify the term (function, design, criteria or constraint) shown or described below: function design criteria constraints launch loads must launch an can use 20 popsicle through the air aluminum foil sticks, 10 elastics and a ball 1 m condiment cup minimum distance 5 Science 8R Designing and Evaluating Mechanical Devices - Questions 1. Identify for each of the following whether they are describing design or function. Function a. A truck is used for transporting passengers and cargo design b. A minivan has seating for 7 people design c. Modern use lighter alloys instead of heavy steel Function d. SUVs need to travel through rough terrain 2. Criteria for evaluating devices should be as specific as possible. For each of the following pairs of statements, choose which criteria (A or B) would be better to use when evaluating the following devices. Device Criteria A Criteria B Best criteria? phone good camera camera at least 10 B megapixels bike costs under $200 cheap A snowboard strong withstands forces up to 500 N B 3. Which stage of the engineering design cycle (diagram on the previous page), is described below? Define the look at the rubric, what will the car be judged on (speed, problem aesthetics, efficiency, etc.) Test the Model measure the distance, speed, etc that the car travels Make a model build the car, making modifications as necessary Reflect and decide whether to keep the design or modify it Redesign Plan solutions plan out the car (draw, list materials)– what gears to use, where to put wheels, how many rubber bands to use,etc. 6 Science 8R Car Technology Timeline Complete the timeline to show how car technology has changed over the past 150 years Change / Event Reason(s) Safety Society Trial Science Environ and and ment Error Engine ering 1886 - first automobile - motorized bike (Benz) ✔ toy for the rich 1900s - in US, many cars were now on the roads ✔ Industrial Revolution made cars cheaper and more readily available 1926 - safety glass ✔ ✔ ✔ Plate glass caused facial injuries Lab accident and repeated experiments/testing Annual model change ✔ Increase slumping car sales 1950s - lap belts (2 point belts) ✔ ✔ Prevented accidents - people colliding wit inside of car, ejection from car Earliest crash safety tests showed safety improvement 1960s - 3-point belts Reduced certain injuries (abdominal, head injuries) 1959 - Crumple zones ✔ ✔ Rigid internal frame protected passengers while crumple zones allowed collision forces to be absorbed based on understanding of force and energy 1950s - Crash test dummies ✔ ✔ Safely test car designs before they get on the market 1966 - National highway transportation standards - ✔ regulated safety Injuries and deaths, senate hearings 7 Science 8R Safety Society Trial Science Environ and and ment Error Engine ering 1980s - Air bags ✔ ✔ ✔ Prevented injuries from hitting dashboard Lab accident repeated experiments to determine safe launching speed 2000s - Next generation air bags severe head injuries from minor accidents 1990s and 2000s hybrid gas electric and fully electric ✔ ✔ cars climate change concerns increasing gas prices 2000s - bluetooth enabled communication ✔ ✔ society demand for connectivity, advances in communication technology 2010s-2020s - Automated cars/self-driving cars ✔ ✔ Driver error is a major cause of collisions advancements in robotics and AI 8 Science 8R Technological Development – Notes Technological development (such as the automobile industry) is influenced by many factors Trial and error Cars are repeatedly rammed into concrete barriers in controlled tests and the damage is measured Crash test dummies are used to simulate human injuries in crash tests Society Fed up with injuries from unrestrained passengers, doctors demanded the introduction of seatbelts in cars Consumer demand for integrated technology has brought the introduction of Bluetooth and GPS systems into cars Scientific Advancements The study of laws of force and motion in collisions led to the use of crumple zones in cars. Environment Climate change concerns have led to gas-electric hybrids 9 Science 8R Mechanical Devices - Notes To qualify as a machine (mechanical device), a tool or device must do one or more of the following things: Change the direction of Take less effort (force Make it faster to do the force advantage) work (speed advantage) Identify the type of pulley shown fixed block and tackle movable 10 Science 8R Identify the simple machine found in the following objects inclined plane lever wheel and axle screw wedge pulley Classes of Levers Diagram Class of 1st 2nd 3rd Lever Examples Teeter totter, pliers, Wheelbarrow, Hockey stick, broom, scissors, crowbar nutcracker baseball bat 11 Science 8R Practice: Identify the class (type) of each of the following levers 3rd class 2nd class 2nd class 1st class 3rd class 1st class 12 Science 8R Term Description Examples Complex/ system in which 2 or bike, car, backhoe compound more simple machines machine work together component a single part in a wheel, seat, bike pedal, chain, frame, mechanical device etc. 13 Science 8R Mechanical Devices - Questions 1. What simple machine(s) can be found in the following common objects? a. chopping b. teeter totter c. cap on a bottle d. flagpole axe wedge and lever lever screw pulley e. door knob f. stairs g. scissors h. steering wheel Wheel and axle inclined plane wedge and lever wheel and axle 2. Identify the type of levers in the diagrams below as first, second or third class levers. (Hint: Identify the load, effort and fulcrum for these objects first). b. a. c. d. class 1 class 3 class 3 class 2 g. f. e. h. class 2 class 3 class 1 class 1 14 Science 8R 3. Answer the following questions using the image below. a. Is this a simple or complex machine? complex b. identify 3 components you would find in it. blade, pedal, metal plate, piston, etc. 4. Answer the following questions using the image below. a. What is the function of this mechanical squeeze an orange device? b. identify 3 different simple machines used wedges (sickle, guillotine blade, in this mechanical device. sword, spike), pulleys (A-B-C), levers (door, boot contraption) 15  Science 8R Force and Speed Advantages – Notes Force advantage Speed Advantage Visual Effect on effort decrease increase required Effect on distance increase decrease required Effect on speed slower faster How it is achieved small effort being distributed large effort being distributed across a longer distance across a shorter distance Uses going up-hill, hauling heavy coasting downhill, sports car, loads, weaklings shooting a puck Simple machines inclined planes, movable Type 3 levers, axle driven wheels pulleys, screw, Type 2 levers, wedge, many wheel and axles Benefits less effort (easier) faster or further Trade-off lose speed or distance more effort (harder) Trade offs: You can’t have both speed advantages and force advantages at the same time. When you gain a force advantage you lose speed advantage and vice versa. Example: Wedges Inclined planes 16 Science 8R Practice: Identify each of the following as having force or speed advantages (or none) force advantage force neither speed force force Which pulley gives you the greatest force #4 (takes least effort) advantage? 17  Science 8R Force and Speed Advantages - Questions 1. Identify the type of advantage (force, speed, neither) each of the following machines would provide. b. c. d. a. neither force neither speed f. h. e. g. force force speed force 2. Which ramp length will give you the greatest force advantage? Longest one 3. What is the disadvantage of a machine with a. A force advantage? Takes longer to do it b. A speed advantage? Takes more effort to do it 18  Science 8R Gears – Notes Type of Gear Multiplying Gear Parallel Gears Reducing Gears Diagram Effect on speed Increase no effect decrease of follower gear Effect on effort of increase no effect decrease driver gear Type of speed Change direction force advantage Uses Coasting downhill change direction/ Going uphill, hauling spacing out gears heavy loads Benefits faster or further less effort (easier) Trade-off more effort (harder) no effect on speed or slower or less distance effort covered Gear Ratio Greater than 1 Equal to 1 Less than 1 𝑑𝑟𝑖𝑣𝑒𝑟 𝑡𝑒𝑒𝑡ℎ 𝑑𝑡 𝑔𝑒𝑎𝑟 𝑟𝑎𝑡𝑖𝑜 = 𝑓𝑜𝑙𝑙𝑜𝑤𝑒𝑟 𝑡𝑒𝑒𝑡ℎ or 𝑔𝑟 = 𝑓𝑡 Idler gear Linkage (chain) added when you need the driving and driven gear to travel in the same direction or to increase the distance between the driving and driven gear 19  Science 8R Gears – Questions 1. Complete the following chart Drawing Type of gear Type of Gear Ratio (round to nearest advantage tenth) 𝑑𝑡 14 a. multiplying speed 𝑔𝑟 = 𝑓𝑡 = 12 = 1. 2 𝑑𝑡 8 b. reducing force 𝑔𝑟 = 𝑓𝑡 = 40 = 0. 2 𝑑𝑡 16 c. parallel neither 𝑔𝑟 = 𝑓𝑡 = 16 =1 𝑑𝑡 40 d. multiplying speed 𝑔𝑟 = 𝑓𝑡 = 24 = 1. 7 e. 𝑑𝑡 20 multiplying speed 𝑔𝑟 = 𝑓𝑡 = 10 =2 𝑑𝑡 80 f multiplying speed 𝑔𝑟 = 𝑓𝑡 = 20 =4 20 Science 8R 2. Answer the following questions Diagram Which way will the clockwise clockwise follower gear turn? What is the gear 𝑔𝑟 = 𝑑𝑡 = 60 =3 𝑓𝑡 20 ratio (nearest 𝑔𝑟 = 𝑑𝑡 = 6 = 0. 6 𝑓𝑡 10 tenth)? What type of advantage does force advantage speed advantage this gear train provide? 3. Answer the following questions Which gear set up in a car would you use to travel at highway speeds? 1A Which gear set up in a truck would you use to haul heavy loads? 3A 21  Science 8R Hydraulics and Pneumatics – Notes Pressure System Pneumatics Hydraulics Function transmits a force using pressurized fluid 𝐹𝑜𝑟𝑐𝑒 (𝑁) 𝐹 𝑝𝑟𝑒𝑠𝑠𝑢𝑟𝑒 = or 𝑝= 𝐴 𝐴𝑟𝑒𝑎 (𝑐𝑚2 ) Type of Fluid used gas such as air liquid Type of system Open – fluid is not sealed in Closed – fluid is sealed in Examples Inflatable slide Car Brakes Respiratory System Backhoe Bike tire pump Circulatory System Air compressor with staple gun Car Lift Visual What type of fluid pressure system is shown? pneumatic system How could you increase the pressure exerted on the table? decrease the area of the release hole 22  Science 8R If a force of 46 N was applied to the piston as you pushed it down, and the area of the piston is 0.50 m², then what would the pressure be inside the cylinder? Diagram Info Formula Substitution Answer (with units) p=? 𝐹 F=46 N 𝑝 = 𝐴 46𝑁 A=0.5 m2 = 2 92 N/m2 or Pa 0.5𝑚 Pascal’s Pressure applied to an enclosed fluid is transmitted equally in all directions Law/Principle (the shape of the container has no effect on pressure) Visual Application to If the area of the output piston is hydraulics much larger than the area of the input piston, then the force on the output piston will be much larger. Thus, a small force can lift a large force (like a car) 23 Science 8R Hydraulics and Pneumatics - Questions 1. Identify the type of fluid pressure system described. a. b. blood pressure cuff hydraulics pneumatics d. Wing flaps and landing gear on modern planes are raised and lowered using liquids c. bouncy castle under pressure pneumatics hydraulics 2. The tip of a hypodermic needle is pressed against someone’s skin with a force of 2 N. If the tip of the needle has an area of 0.000 001 m2 , what is the pressure exerted on the skin by the needle? Info Formula Substitution (with units) Answer p=? 𝑝= 𝐹 = 2𝑁 2 2 000 000 Pa (N/m2) 𝐴 F=2 N 0.000 001𝑚 A=0.000 001 m2 3. Calculate the pressure on piston A. Show ALL steps. 𝐹 𝑝= 𝐴 30 𝑁 = 2 0.2𝑚 150 Pa (N/m2) 24 Science 8R 4. Use the diagram of the inflated tire below to answer the following questions. a. The diagram of the inflated tire seen in this question is displaying what law regarding pressure and fluids? Pascal’s Principle b. Restate the Law: Pressure applied to an enclosed fluid is transmitted equally in all directions 5. Hydraulic lift Which letter denotes the input (effort) A piston? Which letter denotes the output (load B piston) What type of advantage does this give force you? Which piston will move a larger distance? A 6. Hydraulic lifts a. Which figure gives you a greater force advantage and why? figure 2 - larger output piston b. how could you change syringe A to give the hydraulic system a greater force advantage? make it smaller 25  Science 8R Mechanical Advantage – Notes Mechanical advantage (MA) Definition how much your effort force is multiplied by also called force ratio Relationship to force adv. The greater the MA, the greater the force advantage Formula 𝑀𝑒𝑐ℎ𝑎𝑛𝑖𝑐𝑎𝑙 𝐴𝑑𝑣𝑎𝑛𝑡𝑎𝑔𝑒 = 𝐿𝑜𝑎𝑑 𝐹𝑜𝑟𝑐𝑒 (𝑁) or 𝐸𝑓𝑓𝑜𝑟𝑡 𝐹𝑜𝑟𝑐𝑒 (𝑁) 𝐿𝐹 𝑀𝐴 = 𝐸𝐹 Visual MA Less than 1 More than 1 Equal to 1 Type of advantage Speed Force Neither Note: this is OPPOSITE to gear ratio, which is a speed ratio rather than a force ratio #1. Calculate the mechanical advantage of an inclined plane that uses 6 N of force to lift a 10 N object and identify the type of advantage it provides. Round to the hundredths place (two places after the decimal) Info Formula Substitution Answer Type of (with units) Advantage MA=? 𝑀𝐴 = 𝐿𝐹 = 10𝑁 =1.6666666..= force 𝐸𝐹 6𝑁 LF=10 N 1.67 EF=6 N (notice the units cancel out) 26  Science 8R #2: Calculate Info Formula Substitution Answer Type of the mechanical (with units) Advantage advantage of the hydraulic MA=? 𝑀𝐴 = 𝐿𝐹 = 500𝑁 =25 force 𝐸𝐹 20𝑁 press shown LF=500 N EF=20N #3. Calculate Info Formula Substitution Answer Type of the mechanical (with units) Advantage advantage of the lever. MA=? 𝑀𝐴 = 𝐿𝐹 = 20𝑁 =0.04 speed 𝐸𝐹 500𝑁 Round to the LF=20 N hundredths EF=500N place (two places after the decimal) 27  Science 8R Mechanical Advantage - Questions 1. Use the information given to calculate the mechanical advantage of each device. Round to the nearest tenths place (one number after the decimal point) if necessary Diagram/description Info Formula Substitution Answer Type of (with units) Advantage a. MA=? 𝑀𝐴 = 𝐿𝐹 = 300𝑁 6 force 𝐸𝐹 50𝑁 LF=300N 5 EF=50 N lift a 300 N rock with an effort force of 50 N. MA=? 𝑀𝐴 = 𝐿𝐹 = 50𝑁 0.1 speed 𝐸𝐹 500𝑁 LF= 50N EF=500N b. A baseball bat can exert a force of 50 N on the ball when the force applied by a person’s hand is 500 N. c. MA=? 𝑀𝐴 = 𝐿𝐹 = 10𝑁 = 1. 9230… force 𝐸𝐹 5.2𝑁 Input Force = 5.2 N LF=10 N =1.9 Output Force = 10.0 N EF=5.2 N d. MA=? 𝑀𝐴 = 𝐿𝐹 = 40 000𝑁 400 force 𝐸𝐹 100𝑁 LF=40 000 N EF=100 N 28  Science 8R Pulley System Number of supporting ropes MA Show work here 1 1 1 𝐿𝐹 = 100𝑁 𝐸𝐹 100𝑁 2 2 2 𝐿𝐹 = 100𝑁 𝐸𝐹 50𝑁 3 3 3 𝐿𝐹 = 100𝑁 𝐸𝐹 33.33𝑁 4 4 4 𝐿𝐹 = 100𝑁 𝐸𝐹 25𝑁 2. What effect does adding more supporting ropes in a pulley system have on the mechanical advantage of the pulley system? as you increase the number of supporting ropes, you increase the mechanical advantage 3. CHALLENGE (hint: 1kg = 10N) What is the MA of this pulley system? Diagram/description Info Formula Substitution Answer Type of (with units) Advantage MA=? 𝑀𝐴 = 𝐿𝐹 5 force 𝐸𝐹 LF=10 kg x = 100𝑁 20𝑁 10N/kg = 100 N EF=20 N. 29 Science 8R 4. Theoretical Mechanical Advantage of Pulleys a. Which pulley system(s) have a theoretical MA of 2? B and C b. Which pulley system(s) would require the least effort to lift a load? D and E 30 Science 8R Theoretical MA - Notes Theoretical / Ideal Mechanical advantage (TMA or IMA) Definition uses length measurements to predict what the MA of a system should be if there was no friction Relationship to force The greater the MA, the greater the force advantage advantage Formula (for levers) 𝑇𝑀𝐴 = 𝐸𝑓𝑓𝑜𝑟𝑡 𝑎𝑟𝑚 (𝑚) or 𝑇𝑀𝐴 = 𝐸𝐴 𝐿𝑜𝑎𝑑 𝑎𝑟𝑚(𝑚) 𝐿𝐴 Visual Relationship to MA The actual MA will always be less than the TMA because friction reduces efficiency Example: Calculate the TMA of the following lever Diagram Info Formula Substitutio Answer Type of n (with Advantage units) TMA = ? 𝑇𝑀𝐴 = 𝐸𝐴 6𝑚 4 force 𝐿𝐴 1.5𝑚 EA = 6m LA = 1.5 m Given the following data calculate the TMA of each lever Effort arm (cm) Load arm (cm) TMA 20 cm 80 cm 20cm/80 cm = 0.25 50 50 50 cm/50 cm = 1 80 20 80 cm/20 cm = 4 The longer the effort arm, the greater the mechanical advantage of the lever. 31  Science 8R Theoretical MA - Questions 1. Calculate the TMA of each lever below. Round to two decimal places if necessary. Diagram Info Formula Substitution Answer Type of (with units) Advantage TMA = ? 𝑇𝑀𝐴 = 𝐸𝐴 = 20𝑚 10 force 𝐿𝐴 2𝑚 EA = 20 m LA = 2 m a. TMA = ? 𝑇𝑀𝐴 = 𝐸𝐴 = 5𝑚 0.25 speed 𝐿𝐴 20𝑚 EA = 5 m LA = 20 m b. 2. Calculate the MA and TMA of the lever below. Diagram Info Formula Substitution Answer Type of (with units) Advantage TMA = ? 𝑇𝑀𝐴 = 𝐸𝐴 = 3𝑚 TMA = 3 force 𝐿𝐴 1𝑚 EA = 3m LA = 1 m MA=? 𝑀𝐴 = 𝐿𝐹 = 80𝑁 MA = 2 force 𝐸𝐹 40𝑁 LF = 80 N EF = 40 N 3. Challenge: Calculate the MA and TMA of the lever below. TMA = ? 𝑇𝑀𝐴 = 𝐸𝐴 = 1.5 𝑚 TMA = speed 𝐿𝐴 6𝑚 EA = 1.5 m 0.25 LA = 6 m MA=? 𝑀𝐴 = 𝐿𝐹 = 30𝑁 MA = speed 𝐸𝐹 178𝑁 LF = 3kg x 0.17 10 N/kg = 30 N EF = 178 N 32  Science 8R 4. When you compare MA and TMA for a lever, which number is MA always lower? 5. What force accounts for this difference? friction 6. A coyote sets up a class 1 lever so the fulcrum is 0.1 m from a large rock he is trying to lift and 5 m from the place where he will set and try to lift the rock from. a. Calculate the theoretical mechanical advantage of this lever. Show all work. 𝐸𝐴 5𝑚 𝑇𝑀𝐴 = 𝐿𝐴 = 0.1𝑚 = 50 b. The 250 N coyote wishes to lift a 10 000 N rock using the lever. Calculate the actual mechanical advantage required to lift this rock. Show all work. 𝐿𝐹 10000𝑁 𝑀𝐴 = 𝐸𝐹 = 250 𝑁 = 40 c. Will the coyote be able to lift the rock using only his weight with this lever? Explain Yes, since the TMA is at equal to or larger than the MA 33  Science 8R Work – Notes Work Definition the amount of energy transferred by exerting a force over a distance Formula 𝑤𝑜𝑟𝑘 = 𝑓𝑜𝑟𝑐𝑒(𝑁) 𝑥 𝑑𝑖𝑠𝑡𝑎𝑛𝑐𝑒( Make sure the force is measured in or 𝑊 = 𝐹 𝑥 𝑑 NEWTONS and the distance is measured in METRES – if it is not, then you will need to convert it to the proper units Units joules or Newton-metres Relationship to In order for work to be done, force and a force must be applied over distance a distance – if one is not present, then work is not done! What effect change how the work is does simple done but do not decrease machines have the amount of work you do on work done? (for example an inclined plane decreases the force but increases the distance) Example Is a force applied? Is there motion? Doing work? yes no no An upward force is applied to a wooden board. The board does not move. A force is applied to a yes yes yes shopping cart. The cart moves to the right. An upward force yes yes yes is applied to lift a barbell. The barbell moves upward. 34 Science 8R A forklift moves 34m carrying a 1023N box across the warehouse floor. How much work is done by the forklift? Diagram Info Formula Substitution (with Answer (with units) units) W=? 𝑊 = 𝐹𝑥𝑑 = 1023𝑁 𝑥 34𝑚 𝑊 = 34 782 𝑁𝑚 𝑜𝑟 𝐽 F = 1023 N D = 34 m How much work is done by the person pulling the cart? Formula Substitution (with Answer (with units) Info units) W=? 𝑊 = 𝐹𝑥𝑑 = 160𝑁 𝑥 10𝑚 = 1600 𝑁𝑚 𝑜𝑟 𝐽 F = 160 N D = 10 m 35 Science 8R Work - Questions 1. For each of the following, state whether work is being done on the object or not c. a. b. You A man lifting a box to be Man lifting a stone with a push against a wall but placed on the table lever nothing happens to the wall yes no yes 2. An experiment is set up using the identical ramp set at 3 different angles. The effort force and distance were measured and the work calculated. a. What was the manipulated variable in this experiment? angle of ramp b. Use the data (evidence)to make a claim about the effect that the angle of the ramp has on the work it requires to push a car up a ramp. The angle of the ramp has no effect on the work required. The amount of work was the same (4.90 J) when the angle was 30, 45 and 60 degrees. 36 Science 8R 3. Calculate the work done in the following situations. Round to one decimal place if necessary. a. A 15 N box is lifted 0.5 m. Info Formula Substitution (with units) Answer (with units) W=? 𝑊 = 𝐹𝑥𝑑 = 15𝑁 𝑥 0. 5 𝑚 𝑊 = 7. 5 𝑁𝑚 or J F = 15 N D = 0.5 m b. A 500 N table is pushed 200 cm up a ramp Info Formula substitution (with units) Answer (with units) W=? 𝑊 = 𝐹𝑥𝑑 = 500𝑁 𝑥 2 𝑚 𝑊 = 1000 𝑁𝑚 or J F = 500 N D = 200 cm = 2 m c. A pulley is used to lift a 200 kg piano up 10 m. [Hint. Remember that a 1 kg object has a weight of 10 N] Info Formula Substitution (with units) Answer (with units) W=? 𝑊 = 𝐹𝑥𝑑 = 2000𝑁 𝑥 10 𝑚 = 𝑊 = 20 000 𝑁𝑚 or J F = 200 kg x 10N/kg = 2000 N D = 10 m d. Vivian and Christy were having a tug-of-war with their teacher and were trying to pull him 3m. They pulled as hard as they could, but they could not move him! Assuming the teacher’s mass is 90 kg and Vivian and Christy pulled with force of 800 N, how much work did they perform on the teacher? Info Formula substitution (with units) Answer (with units) W=? 𝑊 = 𝐹𝑥𝑑 = 800𝑁 𝑥 0 𝑚 𝑊 = 0 𝑁𝑚 (none, the F = 800 N teacher did not move) D=0m 37 Science 8R 4. Two students use a lever made of a log to push their parent’s car out of the ditch. e. They push down on one end of the lever with 500 N of force. They move their end of the lever about 60 cm. Calculate the work input. Info Formula Substitution (with Answer (with units) units) WI = ? 𝑊 = 𝐹𝑥𝑑 = 500𝑁 𝑥 0. 6 𝑚 = 𝑊𝐼 = 300 𝑁𝑚 𝑜𝑟 𝐽 FI = 500 N DI = 60 cm =0.6 m f. The car weighs 2500 N and has to be moved 10 cm upwards. Calculate the work output. Info Formula Substitution (with Answer (with units) units) WI = ? 𝑊 = 𝐹𝑥𝑑 = 2500𝑁 𝑥 0. 1 𝑚 𝑊𝑂 = 250 𝑁𝑚 𝑜𝑟 𝐽 FI = 2500 N DI = 10 cm =0.1 m 38 Science 8R Energy - Notes Energy the ability to do work Potential (PE) Kinetic (KE) stored – elastic, gravitational, nuclear, motion - mechanical, sound, light, chemical, etc. thermal, electrical, etc. Law of Conservation of Energy: Energy cannot be created or destroyed 39 Science 8R Energy can be transferred from one Energy can be transformed from one form object to another to another energy convertors transform one form of energy to another 40 Science 8R Identify the energy source and energy Energy source Energy Product product(s) in each of the following energy convertors Battery powered flashlight chemical (potential) electrical and light and heat (kinetic) A catapult that uses a rope and spring elastic (potential) mechanical (kinetic energy) Gravitational Potential Energy The energy stored in an object due to its height above the Earth’s surface. 41 Science 8R Energy conversions in Falling objects using the law of conservation of energy Energy conversions on hills 42 Science 8R a. At which point does the cart B have the highest kinetic energy? b. At which point does the cart A have the highest potential energy? c. What energy conversion is potential occurring between points A and to B? kinetic Transformation of energy in a pendulum At which point(s) does the ball have the highest potential energy? 1 and 5 At which point(s) does the ball have the lowest potential energy? 3 At which point(s) does the ball have the highest kinetic energy? 3 At which point(s) does the ball have the lowest kinetic energy? 1 and 5 43 Science 8R Energy Questions 1. Identify the energy source and energy Energy source Energy Product product(s) for the following energy convertors chemical mechanical and (potential) heat (kinetic) a. b. Diving converts gravitational gravitational mechanical and potential energy into mechanical (potential) sound (kinetic) kinetic and sound energy 2. Identify which picture best demonstrates potential energy and which best demonstrates kinetic energy in the slingshot below. a. b. potential kinetic 3. Use the diagram of the diver below to identify at which point the diver has the a. highest potential energy? A b. lowest potential energy? C c. highest kinetic energy? C d. lowest kinetic energy? A 44 Science 8R 4. Use the diagram of the roller coaster below to answer the questions below. A coaster is moved to the top of the highest hill a. at which point does the coaster have F and allowed to roll freely. the least kinetic energy? b. at which point is potential energy G being transformed to kinetic energy c. at which point does the coaster have F the most potential energy? d. at which point is kinetic energy being K transformed to potential energy? 5. Use the law of conservation of energy to determine the amount of potential and kinetic energy in a pendulum at different points Kinetic energy Potential Energy A 0J 2.4J B 2.0 J 0.4 J C 2.4 J 0J D 0J 2.4 J 6. A ball is thrown upwards A B a. Which graph shows the proper energy forms immediately after the ball is A thrown? b. Which graph shows the proper energy forms when the ball is at its B maximum height? 45  Science 8R Efficiency – Notes Identify the energy source and Energy source Energy Product energy product(s) in each of the following energy convertors electrical (potential) mechanical and heat (kinetic) popsicle stick catapult elastic (potential) mechanical (kinetic) Efficiency Description How good a machine is at converting energy to usable form Percentage of input energy (energy sources) that is transferred into useful output energy (energy products) Units Percentage (%) Formula 𝑤𝑜𝑟𝑘𝑜𝑢𝑡𝑝𝑢𝑡 𝑤𝑜 𝑒𝑓𝑓𝑖𝑐𝑖𝑒𝑛𝑐𝑦 = 𝑤𝑜𝑟𝑘𝑖𝑛𝑝𝑢𝑡 𝑥100% or 𝑒𝑓𝑓 = 𝑤𝑖 𝑥100% *** Remember that often you have to calculate work input and output first by multiplying force by distance Low efficiency much of the input energy is “wasted” or changed into unusable forms of energy High efficiency Most of the input energy is changed to useful output energy Friction The resistance that one surface or object encounters when moving over another. 46  Science 8R Factors affecting efficiency Friction is the main cause of inefficiency Friction produces thermal energy and sound energy, which in most cases, is wasted energy We can make machines more efficient by reducing friction by: Using fewer moving parts Use smoother materials Oiling or greasing moving parts Example 1 : Calculate the efficiency of a gasoline engine, which produces 10 J of work for every 50 J of work that goes into it. Info Formula Substitution (with units) Answer (with units) Wi=50 J 𝑤𝑜 𝑒𝑓𝑓 = 10𝐽 𝑥100% 𝑒𝑓𝑓 = 20% 𝑒𝑓𝑓 = 𝑥100% 50𝐽 Wo=10 J 𝑤𝑖 Eff = ? Example 2: Calculate the efficiency of the following inclined plane. Info Formula Substitution (with units) Answer (with units) Eff = ? 𝑒𝑓𝑓 = 𝑤𝑜 𝑥100% = 200𝐽 𝑥100% 𝑒𝑓𝑓 = 80% 250𝐽 WI = 250 J 𝑤𝑖 Wo = 200 J 47 Science 8R Efficiency – Questions 1. Identify the energy sources and products for the following. convertor energy source energy product(s) electrical (potential) radiant/light and heat (kinetic) skiing down a hill gravitational (potential) mechanical (kinetic) 2. You are trying to move a heavy rock. The pulley system is 87% efficient, the inclined plane is 56% efficient and the lever is 84%. a. Which simple machine is most efficient? Pulley b. What percent of energy is wasted in the 44% (100-56) inclined plane? c. What force causes inefficiency in most friction machines? d. How can you improve efficiency in mechanical Reduce friction by lubricants, systems? waxing, using wheels, etc. 3. For each of the following predict the likely effect on efficiency (increase, decrease or no effect) a. adding wheels to a suitcase you are dragging up a ramp increase b. switching to studded car tires in the winter decrease c. oiling squeaky door hinges increase d. making a longer ramp no effect 48 Science 8R 4. A person puts in 1650 J of work to push a box up the ramp. The work output of the ramp is 1430 J. What is the efficiency of the ramp? Round your answer to the nearest whole number. Info Formula Substitution (with units) Answer (with units) Wi=1650 J 𝑤𝑜 = 1430𝐽 𝑥100% 𝑒𝑓𝑓 = 86. 6666 = 87% 𝑒𝑓𝑓 = 𝑥100% 1650𝐽 Wo=1430 J 𝑤𝑖 Eff = ? 5. Calculate the efficiency. Round your answer to the tenth place if necessary. a. Info Formula Substitution (with units) Answer (with units) Eff = ? 𝑤𝑜 𝑒𝑓𝑓 = 5.0𝐽 𝑥100% 𝑒𝑓𝑓 == 96. 153… = 96. 2 𝑒𝑓𝑓 = 𝑥100% 5.2𝐽 WI = 5.2 J 𝑤𝑖 Wo = 5.0 J b. Calculate Efficiency: Show all work 𝑤𝑜 1400 𝐽 𝑒𝑓𝑓 = 𝑤𝑖 𝑥100%= 1600 𝐽 𝑥100%= 87.5% 49  Science 8R Formulas 1 kg = 10 N 𝑑𝑟𝑖𝑣𝑒𝑟 𝑡𝑒𝑒𝑡ℎ 𝑑𝑡 𝑔𝑒𝑎𝑟 𝑟𝑎𝑡𝑖𝑜 = 𝑓𝑜𝑙𝑙𝑜𝑤𝑒𝑟 𝑡𝑒𝑒𝑡ℎ or 𝑔𝑟 = 𝑓𝑡 𝐹 𝑝𝑟𝑒𝑠𝑠𝑢𝑟𝑒 = 𝐹𝑜𝑟𝑐𝑒 𝐴𝑟𝑒𝑎 or 𝑝= 𝐴 𝐸𝑓𝑓𝑜𝑟𝑡 𝑎𝑟𝑚 𝐸𝐴 𝑇ℎ𝑒𝑜𝑟𝑒𝑡𝑖𝑐𝑎𝑙 𝑀𝑒𝑐ℎ𝑎𝑛𝑖𝑐𝑎𝑙 𝐴𝑑𝑣𝑎𝑛𝑡𝑎𝑔𝑒 = 𝐿𝑜𝑎𝑑 𝑎𝑟𝑚 or 𝑇𝑀𝐴 = 𝐿𝐴 𝐿𝑜𝑎𝑑 𝐹𝑜𝑟𝑐𝑒 𝐿𝐹 𝑀𝑒𝑐ℎ𝑎𝑛𝑖𝑐𝑎𝑙 𝐴𝑑𝑣𝑎𝑛𝑡𝑎𝑔𝑒 = 𝐸𝑓𝑓𝑜𝑟𝑡 𝐹𝑜𝑟𝑐𝑒 or 𝑀𝐴 = 𝐸𝐹 𝑤𝑜𝑟𝑘 = 𝑓𝑜𝑟𝑐𝑒 𝑥 𝑑𝑖𝑠𝑡𝑎𝑛𝑐𝑒 or 𝑊 = 𝐹 𝑥 𝑑 𝑤𝑜𝑟𝑘𝑜𝑢𝑡𝑝𝑢𝑡 𝑤𝑜 𝑒𝑓𝑓𝑖𝑐𝑖𝑒𝑛𝑐𝑦 = 𝑤𝑜𝑟𝑘𝑖𝑛𝑝𝑢𝑡 𝑥100% or 𝑒𝑓𝑓 = 𝑤𝑖 𝑥100% Table of units Force MA TMA Effort arm Load arm Gear ratio Area Distance Work Pressure Efficiency no units no cm or m cm or m no units m2 m (or Nm Pa or % N units cm) or J N/m2 50