Test on Work, Energy, and Simple Machines Set A

Question 1 of 3: A graph of force versus displacement for an object that moves from rest along a straight, horizontal line is shown. The mass of the object is 2 kg. At which labeled part of the graph is the work done on the object the greatest?

• A

• B

• C

• D

Question 2 of 3: A graph of force versus displacement for an object that moves from rest along a straight, horizontal line is shown. The mass of the object is 2 kg. What is the change in kinetic energy (in joules) of the object at the end of 20 meters? Express the answers as a whole number. No need to write the unit.

Question 3 of 3: A graph of force versus displacement for an object that moves from rest along a straight, horizontal line is shown. The mass of the object is 2 kg. What is the speed (in m/s) of the object at the end of 20 meters? Express the answers in 2 significant figures. No need to write the unit.

Question 1 of 2: A 20-kg box is moved 10 meters across the floor from rest. Two forces were acting on the box while it was displaced as shown. What is the total work (in joules) done on the box? Express the answer as a whole number. No need to write the unit.

Question 2 of 2: A 20-kg box is moved 10 meters across the floor from rest. Two forces were acting on the box while it was displaced as shown. If it took 20 seconds to move the box, how much was the power input in watts? Express the answer as a whole number. No need to write the unit.

Question 1 of 2: Two cars that are moving along horizontal roads are going to be stopped by plowing into identical barriers. Both of the cars are of the same size and shape, but they are carrying loads with different masses. Both of the cars are going to be stopped by the same constant force by the barrier. Which car will have greater work done on it? Justify your answer.

• Car D, because it has a greater mass.

• Car A, because it has greater initial speed.

• Car D, because it has greater initial kinetic energy.

• Car A, because it has greater initial kinetic energy.

Question 2 of 2: Two cars that are moving along horizontal roads are going to be stopped by plowing into identical barriers. Both of the cars are of the same size and shape, but they are carrying loads with different masses. Both of the cars are going to be stopped by the same constant force by the barrier. Which car will require a greater distance to stop? Justify your answer.

• Car A, because it has greater initial speed.

• Car D, because it has greater mass.

• Car A, because it has greater change in kinetic energy.

• Car D, because it has greater change in kinetic energy.

Which machine has the least mechanical advantage?

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• All have the same mechanical advantage.

Which inclined plane has the least ideal mechanical advantage?

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• All have the same ideal mechanical advantage.

Information on the work input and work output on four machines are shown below. Which machine is the least efficient?

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