Forces & Motion PDF

What do I think that I know about Starter: Our new SOI: the topic of this We can measure unit? physical movement and What would I like apply our understanding...

What do I think that I know about Starter: Our new SOI: the topic of this We can measure unit? physical movement and What would I like apply our understanding to know, find out, to keep us safe. or be able to do What immediate in this unit? questions or concerns do I have about this Unit 2: Motion unit? - Identify motion or forces in sports or other areas - Review looking at motion Open ‘Manager’ on your computer Install Vernier Graphical Analysis Connect the motion sensor to the labquest mini and then your computer Open Graphical Analysis Choose ‘sensor data collection’ Choose ‘Add Graph Match’ Start with a position graph Stand in front of the motion sensor, press ‘Collect’ and move to match the graph Challenge levels Create new match graphs and advance through the levels Level 1 (Novice) - Match the graph while watching the screen Level 2 (Intermediate) - Have a partner look at the screen and give verbal instructions Level 3 (Expert) - Study the screen and make some notes. Match the graph from your notes. You can use tape measures and stopwatches Level 4 (Genius) - Do all of the above with velocity graphs Motion graphing stories How can motion be shown on a graph? Why might it be useful for scientists to graph motion? Let’s graph 2 together. Then choose three of your own to graph. Use a pencil. Pause the video before the answers are shown. Add your correction in a colored pen.  Reading the graph A train is travelling along a straight track. Initially, the train is moving to the right. The graph shows the velocity of the train at different times.  Reading the graph 1. What is the velocity of the train at each time? Use the graph to match a velocity to each time. 10 m/s to the right 10 s 6 m/s to the right 0s 5 m/s to the right 20 s 0 m/s 40 s 5 m/s to the left 30 s 6 m/s to the left 45 s 10 m/s to the left  Reading the graph 1. What is the velocity of the train at each time? Answers: 10 m/s to the right 10 s 6 m/s to the right 0s 5 m/s to the right 20 s 0 m/s 40 s 5 m/s to the left 30 s 6 m/s to the left 45 s 10 m/s to the left  Reading the graph 2. At what time is the train moving at each velocity? Use the graph to match the correct time to each velocity. 0s 28 s 6 m/s to the right 12 s 4 m/s to the right 36 s 2 m/s to the right 25 s 0 m/s 15 s 2 m/s to the left 24 s 4 m/s to the left 50 s 6 m/s to the left 16 s 44 s  Reading the graph Home 2. At what time(s) is the train moving at each velocity? Answers: 0s 28 s 6 m/s to the right 12 s 4 m/s to the right 36 s 2 m/s to the right 25 s 0 m/s 15 s 2 m/s to the left 24 s 4 m/s to the left 50 s 6 m/s to the left 16 s 44 s  Telling the story 1. This graph shows part of Sammy’s journey to the shops.  Telling the story 1. What is the best description of Sammy’s journey? A Sammy walks up a hill, along the level, and then down a steeper hill. Sammy walks at a steady speed, stops for a bit, and then returns home at a B steady speed, faster than before. Sammy gradually speeds up, walks at a steady speed, and then slows down C quickly. Sammy gradually speeds up, stops for a bit, then returns home, slowing down D on the way.  Telling the story 2. Sammy goes for a walk on another day. The graph shows her journey.  Telling the story 2. What is the best description of Sammy’s journey? A Sammy walks down a hill. B Sammy walks at a steady speed. Sammy walks quickly, gradually slows down, stops and turns around. C On the way back, she speeds up again. Sammy walks at a steady speed, then turns around and walks back at a D steady speed. Sammy walks quickly, gradually slows down and stops. She then starts E walking again and speeds up as she goes.  Acceleration is a measure What is the unit of how much the speed is of changing in time. acceleration? How do we measure a change in speed? - I can explain the meaning of acceleration - I can calculate acceleration using the equation a = ∆v / ∆t - I can find the acceleration of an object from its velocity-time graph What is happening in each situation? What is happening in each situation? Constant speed Speeding up Slowing down What would the diagram look like for an object that was speeding up faster? What does it mean to speed up faster or slower? Constant speed Time t(s) Position s (m) Speed v (m/s) 0 0 +1 0 1 1 1 +1 +0 2 2 1 +1 +0 3 3 1 Every second, a distance of 1 m is covered → There is a constant speed of 1 m/s during each second → The speed does not change in time → Acceleration = 0 Speeding up Time t(s) Position s (m) Speed v (m/s) 0 0 +1 0 1 1 1 +2 +1 2 3 2 +3 +1 3 6 3 Every second, there is 1 m of distance more covered than the previous second The speed increases with 1 m/s, every second → The acceleration is 1 m/s/s (= 1 m/s2) *Read 1 m/s/s as “one meter per second, per second”* Slowing down Time t(s) Position s (m) Speed v (m/s) 0 0 +3 0 1 3 3 +2 -1 2 5 2 +1 -1 3 6 1 Every second, there is 1 m of distance less covered than the previous second The speed decreases with 1 m/s, every second → The acceleration is -1 m/s/s (= -1 m/s2) *Read 1 m/s/s as “one meter per second, per second”* Acceleration = A measure for how much the speed of an object changes every second Symbol: a Unit: m/s/s or m/s2 Graphically: slope of the velocity-time graph Acceleration Graphically: slope of the velocity-time graph What is the acceleration for each section of the motion? What is the acceleration for each section of the motion? A: ∆v = 3 m/s and ∆t = 2 s so a = 1.5 m/s/s B: ∆v = 0 m/s and ∆t = 2 s so a = 0 m/s/s C: ∆v = 6 m/s and ∆t = 1 s so a = 6 m/s/s D: ∆v = 2 m/s and ∆t = 4 s so a = 0.5 m/s/s If the object suddenly had to stop at t = 10 s, what would the acceleration be between t = 9 s and t = 10 s? If the object suddenly had to stop at t = 10 s, what would the acceleration be between t = 9 s and t = 10 s? The object would have to change its speed from 11 m/s to 0 m/s in 1 second so: ∆v = 0 - 11 m/s = - 11 m/s ∆t = 1 s a = - 11 m/s/s  Thinking about acceleration 1. How does the acceleration of the red car compare to the acceleration of the blue car? A The acceleration of the red car is two times bigger. B The acceleration of the red car is the same size. C The acceleration of the red car is two times smaller.  Thinking about acceleration 2. How does the acceleration of the red car compare to the acceleration of the blue car? A The acceleration of the red car is two times bigger. B The acceleration of the red car is the same size. C The acceleration of the red car is two times smaller.  Thinking about acceleration 3. How does the acceleration of the red car compare to the acceleration of the blue car? A The acceleration of the red car is two times bigger. B The acceleration of the red car is four times bigger. C The acceleration of the red car is the same size. D The acceleration of the red car is two times smaller.  Thinking about acceleration Home 4. How does the acceleration of the grey car compare to the acceleration of the green car? What do you think about the magnitude of the acceleration? A The acceleration of the grey car is two times bigger. B The acceleration of the grey car is the same size. C The acceleration of the grey car is two times smaller. D The acceleration of the grey car is zero. Slowing down and speeding up Using the motion sensor set up we looked at earlier we will look at changing motion. 1. Slowing down - push the trolley gently towards the sensor. Practice a few times so it rolls to a halt before the sensor. Predict what you expect the position time graph and velocity time graph to look like, then collect data. 2. Attach a balloon to the trolley and pump it up. Release it so it travels away from the sensor. Predict what you expect the position time graph and velocity time graph to look like, then collect data. 3. Now hold the sensor high above the head of someone in the group and have them do a vertical jump. Predict what you expect the position time graph and velocity time graph to look like, then collect data. All three of these situations involved changing motion Why did the motion change? What changes could you make to the situation and how would these changes show in the graphs? How might these situations be like some more realistic situations in sports or activities?  A force is an external push or pull on an object. What types of forces do you know? How do forces affect motion? - I can explain what is meant by the term ‘resultant force’ - I can calculate the resultant force - I can describe the effect the resultant force has on an object’s motion Force diagrams: Forces are vectors so it has a magnitude (a certain size) All force arrows start at and a direction. We represent then on diagrams in the the centre of mass. form of an arrow. The magnitude is represented by the length of the arrow The head of the arrow shows the direction of movement. Force is measured in newtons (N). How can we calculate a resultant force? Often, more than one force is acting on an object. The resultant force is the sum of all the forces that act on an object. * You might also sometimes hear “net force” which means the same thing as resultant force or sum of the forces. Up → + Down → - Reaction force: + 10N Gravity: -10N → Resultant force = 10 N + (- 10 N) = 0 N How does the resultant force affect movement? Resultant force Effect Equals zero Object remains still (Balanced forces) Object moves at a constant (same) speed Does not equal zero Acceleration (gets faster) (Unbalanced forces) Deceleration (gets slower) Changes direction How about this example? What is the resultant force and the direction of movement? Complete the practice questions. Plenary: The forces are pushing against each other The biggest force pushes forwards The difference in the forces = the big force – the small force = 60 -15 = 45 The resultant force is 45 N forwards The forces are both push forwards. They add together. The resultant force = 40 + 10 = 50 The resultant force is 50 N forwards Reading task Read this chapter up to page 37 and take notes about forces in action. Effective notes include: Images or diagrams Colour - highlight key terms Mind/concept maps Who wants to skydive? Describe the forces that act on a skydiver as they fall to the ground. Describe how the skydiver’s speed & acceleration changes. You should sketch & annotate a diagram with force arrows. You may conduct research to find out what forces act on the skydiver.  Starter: Who was Isaac Newton? Why is he significant? Newton’s Laws of Motion - Describe Newton’s three laws of motions - Plan an investigation into Newton’s Second Law Newton’s first law: If an object is at rest or moving at a constant speed in a straight line, it will remain at rest or keep moving in a straight line at constant speed unless it is acted upon by a resultant force. Newton’s third law: When two objects interact, they apply forces to one another that are equal in magnitude and opposite in direction (this is also known as the law of action and reaction). Newton’s second law: An object with a large mass requires more force to accelerate than those with a smaller mass. It also means that if the force acting on an object increases, the acceleration increases (which means force and acceleration are proportional). Force = mass x acceleration  Recall our SOI: We can measure physical movement and apply our understanding Starter: What to keep us safe. safety features do you know of in our cars? Movement, safety & sports - Describe the safety features our cars have to prevent injuries in an accident - Explain how these prevent injuries with reference to forces & energy - Practice calculations of Newton’s Second Law What features do our cars have? Modern cars have safety features that absorb kinetic energy in collisions. These typically include: seat belts air bags crumple zones Why are cars built to crumple? How have our cars improved over the years? Understanding car crashes - basic physics: Task: Read the textbook pages linked on Google Classroom. 1. Explain how seatbelts demonstrate Newton’s laws of motion. 2. Explain how airbags demonstrate Newton’s laws of motion. 3. Explain how crumple zones demonstrate Newton’s laws of motion. 4. Answer questions 1-10 on forces in sport at the end. Extension: 1. How could you apply what you have read to what you know about rollercoasters? 2. Research new technological improvements that have been added recently to cars. How do these work? Self-assess: When a professional golfer hits a good tee shot, the ball reaches a speed of 70 m/s in about 0.50 millisecond. (A millisecond is one-thousandth of a second.) A golf ball has a mass of 47 g. a Calculate the acceleration of the golf ball in the first 0.50 millisecond. 70 / 0.0005 = 140,000m/s2 b Calculate the force the golf club exerts on the golf ball. 0.047 (need to change unit) x 140,000 = 6580 kg m/s2 c Predict what will happen to the golf club during the impact. Are you likely to notice any change in the motion of the club? Discuss. The club will continue to accelerate but at a slower rate due to the reaction force from the golf ball (Newton’s 3rd Law). Two ice-skaters, Lee and Melanie, are standing face-to-face when Melanie pushes Lee with a force of 30 kg m/s2. This push causes Lee to accelerate backwards. a What will happen to Melanie? Why? She will also accelerate backwards because there will be an equal and opposite force from Lee pushing on Melanie (Newton’s 3rd Law). b If Lee has a mass of 65 kg and Melanie has a mass of 60 kg, predict whether Melanie’s acceleration will be the same as, smaller or larger than Lee’s acceleration. Justify your answer. Since F =ma & she has a slightly lower mass, her acceleration will be slightly more since F is the same for both skaters. When a skydiver jumps from a plane, the gravitational force acting on them causes them to accelerate straight down towards the centre of the Earth. Air resistance is the force that acts on the skydiver’s body in the opposite direction to this motion. This force increases as the speed of the fall increases. Explain how skydivers use air resistance to manoeuvre into formations and how the parachute works to slow the jumper to a safe landing speed. As the speed increases, the air resistance will also increase. When resistance is equal to gravitational force, acceleration will be zero and the skydiver has reached a constant velocity called the terminal velocity. A parachute covers a much larger area and hence resistance is greater, so terminal velocity is much less. Skydivers can change position so the net air resistance is not vertical, and hence can change direction, in the same way that the sails of a yacht can direct wind to change direction.  Starter: Any skateboarders? What forces and energy are at play when skateboarding? Energy in Motion Learning objectives: - Describe the relationship between kinetic and potential energy - Complete bar graphs representing energy transformations - Describe what happens when friction increases What forms of energy can you spot in different objects in this image? First Law of Thermodynamics (Law of the Conservation of Energy) Energy cannot be created or destroyed, but can be converted into different forms. Skate park simulation - let’s see how energy transforms when skateboarding! Complete the handout. 🛹 Start with “Intro”. Turn ‘on’ the bar graph to see kinetic and potential energy and drag & drop the skateboarder on the track. Change the mass. What happens? 🛹 Try “Friction” simulation. Explore changes that happen when mass or friction are adjusted. 🛹 Try “Playground” to make your own track and test kinetic and potential energy. In your notebook: 1. Describe when potential energy is highest 2. Describe when kinetic energy is highest 3. Describe how kinetic energy and potential energy are related What is kinetic energy? Kinetic energy is the energy an object has because of its motion. All moving things have kinetic energy. To accelerate an object (make it move faster), we need to apply a force (N) which requires work. That energy is then transferred to the object. What is gravitational potential energy (GPE)? Gravitational potential energy is the potential energy an object has because of its location/height in a particular gravitational field.  An osprey with a mass of 2 kg flies at a height of 200 m above the ground. How much gravitational potential energy does the osprey have? GPE = mass x gravitational field strength x height = 2 x 10 x 200 = 4,000 J Rearranging the formulae: Practice Question 1: A high jumper has a mass of 62kg. She jumps to a max height of 2.3m. What is her gravitational potential energy? Practice Question 2: A cheetah can run with a speed of 34 m/s and has a kinetic energy of 32946 J. What is the cheetah’s mass? Practice Question 3: A 20 g stone is a) What is the kinetic energy when the stone hits the bottom of the well? dropped down a well. b) What is the gravitational potential When it hits the energy of the stone at the top of the bottom, it has a speed well? of 20 m/s. c) Calculate the height of the well Kinetic energy & Gravitational potential energy Take notes from the following two pages. Make sure you have & understand the formula in your notebook. What is kinetic energy? What is gravitational potential energy?  Challenge: How Starter: Which sports might the injuries are likely to have relate to physics and more injuries? forces? Collisions in sports Apply knowledge of the physics of collisions and forces to help reduce the number of injuries that can occur from sports Collecting, using and analyzing data (ATL skill) Creating citations, and constructing a bibliography (ATL skill)