Date:____________________________ Name: ________________________________ PHYSICS 11: Work & Power Extra Practice Problem 1: How long will it take a 50 kg girl that can generate 935 W to run up a flight of stairs that are 4.5 m high? Problem 2 : How much work is done by the Earth’s gravitational field on a 10.0 kg mass when the mass drops a distance of 5.0 m? 2 Problem 3 : A 2.0 kg puck accelerated at 5.0 m/s for 0.50 m across a frictionless air hockey table. How much work was done on the puck? Problem 4: A bulldozer pushed a large rock with a force of 5000 N at 2.0 m/s for 20 s. How much work was done? Problem 5: How much power does a crane develop doing 60 000 J of work in 5.00 minutes? Problem 6: A 4.00 kg rubber ball drops from a height of 5.00 m to the ground and bounces back to a height of 3.00 m. (a) How much potential energy does the ball lose on the trip down? (b) How much potential energy does the ball regain on the trip back up? (c) What is the net loss of potential energy during the bounce? Problem 7: A 0.50 kg rubber ball is thrown into the air. At a height of 20 m above the ground, it is traveling at 15.0 m/s. (a) What is the ball’s kinetic energy? (b) What is its gravitational potential energy relative to the ground? (c) How much work was done by someone at ground level throwing the ball into the air? Problem 8: An airplane passenger carries a 300.0N suitcase up the stairs, a displacement of 5.50 m vertically and 3.75 m horizontally. How much work does the passenger do? Problem 9: A steel ball with mass 5.0 kg is at rest on a smooth, level surface. A constant force acts on it through a distance of 10.0 m causing it to roll at 25 m/s. What is the magnitude of the force? Problem 10: A 1200.0kg car speeds up from 16.0 m/s to 20.0 m/s. How much work was done on the car to increase its speed? Problem 11: The amount of output work required to lift a crate with a pulley system is 2200 J. The effort force on the pulley is 40 N. What is the effort distance in meters? Problem 12: a.) If you push an object twice as far while applying the same force, you do ___________________ as much work. b.) If you push an object just as far while applying twice the force you do ___________________ as much work. c.) if you lift an object twice as high at a constant velocity, you do ___________________ as much work. Problem 13: A 1.20 x 103 kg block starting from rest is accelerated by a 2.20 x 103 N force for a distance of 50.0 m along a horizontal surface. a) How much work was done on the mass? b) What is the final velocity of the mass? Problem 14: How long will it take a 50 kg girl that can generate 935 W to run up a flight of stairs that are 4.5 m high? Problem 15: A car engine exerts a force of 4000 N to accelerate the car over a displacement of 100 m in 8.0 s. Calculate the power of the engine. Problem 16: A car of mass 2000 kg is travelling at 45.0 m/s when the driver spots a policeman ahead. The driver applies the brakes lightly for 3.0 s until he slows down below the speed limit. If the average force applied by the brakes was 1.4 x 104 N, by how much did the kinetic energy of the car change? Problem 17: How much energy is consumed by a 100.0 W light bulb if is left on for 12.0 h? Problem 18: Ms. Christy pushes a box of bananas up a hill (see image). She pushes with a force of 10 N up the frictionless incline and takes a break after 2m (a horizontal displacement of 1.5m). She then pushes up another 3 m to the top of the hill with the same force. Calculate the total work done on the box by Ms. Christy when she reaches the top of the hill.