Simple Machines & Work PDF

Work or no work? Work or no work? Let's practice: A crane uses an average force of 5200 N to lift a girder 25m. How much work does the crane do on the girder? W=F x D W= (5200N) x (25m) W=130000 J  Let's practice: The brakes on a bicycle apply 125 N of frictional force to...

Work or no work? Work or no work? Let's practice: A crane uses an average force of 5200 N to lift a girder 25m. How much work does the crane do on the girder? W=F x D W= (5200N) x (25m) W=130000 J  Let's practice: The brakes on a bicycle apply 125 N of frictional force to the wheels as the bicycle travels 14m. How much work have the brakes done on the bicycle? W=F x D W= (125N) x (14m) W=1750 J  Simple Machines © The Science Duo  Simple Machines A device that has few or no moving parts Makes work easier (does not reduce the amount of work done) Examples - lever, inclined plane, pulley, wheel and axle, screw, and wedge Compound Machines – made up of two or more simple machines  Lever A rigid bar that is free to pivot on a fixed point Fulcrum – a point at which the lever pivots Load – the object being lifted Effort – the force applied to make the object move Lever Load Effort = 25 N Fulcrum  Types of Levers First Class – the fulcrum is located between the effort and the load Second Class – the load is located between the fulcrum and the effort Third Class – the effort is located between the fulcrum and the load Seesaw Wheelbarrow Shovel  Inclined Plane Also referred to as a ramp A flat, slanted surface Reduces the force needed to move an object by increasing the distance moved  Pulley A grooved wheel with a rope, chain, or cable wrapped around it Change the direction of the force Flagpole Elevator Construction Crane  Types of Pulleys Fixed pulley – attached to a structure; must use greater effort than the load (ex. flagpole) Movable pulley – attached to an object you want to move; requires less effort to move a load (ex. elevators) Compound pulley – uses a fixed and movable pulley; the amount of effort is less than half of the load (ex. construction cranes)  Wheel and Axle Two circular objects that are fastened together and rotate around a common axis Wagon Bicycle Car  Screw An inclined plane wrapped around a cylinder Drill Bit Jar Lid Corkscrew  Wedge A device that is thick at one end and tapers to a thin edge at the other end Axe Doorstop End of a Shovel  Checkpoint 6 checkpoint questions Discuss each question with a partner Write a complete answer to each question on your notes page  Question 1 Describe a situation in which using a simple machine would be helpful.  Question 2 Would a longer or shorter inclined plane be better to use? Explain.  Question 3 Describe how you use simple machines on a daily basis.  Question 4 Identify the simple machine. Teeth  Question 5 Identify the simple machine. Skateboard  Question 6 Identify the simple machine. Stapler