Work equals —

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A. force times speed
Incorrect. That is not the formula for work.

B. speed times distance
Incorrect. That is not the formula for work.

C. force times distance
Correct!

D. mass times distance
Incorrect. That is not the formula for work.

In order for work to be done —

A. an object must fall
Incorrect. An object does not have to fall in order for work to be done.

B. an object must be pushed
Incorrect. An object does not have to be pushed in order for work to be done.

C. force must be applied to an object
Incorrect. Even though a force has been applied, work has not been done unless the object moved in the direction of the force.

D. an object must move in the direction that the force is applied
Correct!

In which picture is work being done?

A. Picture A
Incorrect. Remember, in order for work to be done, the direction of the motion of an object must be the same as the force applied to the object.

B. Picture B
Correct!

C. Picture C
Incorrect. Remember, in order for work to be done, the direction of the motion of an object must be the same as the force applied to the object.

D. Picture D
Incorrect. Remember, in order for work to be done, the direction of the motion of an object must be the same as the force applied to the object.

How do machines help make work easier?

A. Machines change the distance an object travels; therefore, they decrease the amount of work needed to move the object.
Incorrect. Machines do not decrease the amount of work.

B. Machines change the size, distance, or direction of the force you have to exert in order to do work.
Correct!

C. Machines change the mass of an object; therefore, they make the work easier.
Incorrect. Machines change the size, distance, or direction of the force you have to exert in order to do work.

D. Machines increase the amount of input force needed to do work, and this makes work easier.
Incorrect. If the amount of input force was increased this would not make work easier.

In the diagrams below, the box is being moved from point Y to point Z. How do the two pictures below differ?

A. The amount of input force required would be less in picture 2 than in picture 1.
Correct! When using an inclined plane to do work, the input force needed to move the object is less.

B. The amount of work completed is less in picture 2 than in picture 1.
Incorrect. The amount of work does not change when work is done using a simple machine such as an inclined plane.

C. The mass of the object in picture 2 is less than in picture 1.
Incorrect. The mass does not change when work is done using an inclined plane.

D. No work is being done in picture 2, but there is work being done in picture 1.
Incorrect. There is work being done in picture 2 but the input force needed to do the work would be less using the simple machine.