Work - Kinetic and Gravitational Potential Energy

Which of the following sentences uses work in the scientific sense?

• Stan goes to work on the bus.

• Anne did work on the project for 5 hours.

• Joseph found that holding the banner in place was hard work.

• An engine does work on a car when the car is moving.

Work is done on an object

• whenever a force acts on the object.

• whenever a force acts at 90^o to the displacement of the object.

• whenever a force causes a displacement of the object.

• whenever a net force acts on the object.

In which of the following cases is NO work done?

• A weightlifter lifts a barbell.

• A weightlifter holds a barbell overhead.

• A weightlifter slowly lowers a barbell.

• A weightlifter drops a barbell and the barbell falls to the ground.

If the sign of work is negative, (choose two)

• the force is in the same direction as the displacement.

• the force is acting at 90^o to the displacement.

• the component of the force that does work is the direction opposite to the displacement.

• the force acts in the opposite direction to the displacement.

A painter lifts a bucket of paint, carries it 5 m horizontally, then sets it back down. Which of the following is true?

• The force of gravity does negative work when the worker lifts the bucket.

• The painter does positive work on the bucket when carrying it horizontally at constant speed.

• The painter does positive work on the bucket when setting it down.

• No net work is done on the bucket.

Which equation is used to calculate the work done on an object by a force at an angle,  $\theta$  , to the displacement?

•  $W=Fd$  

•  $W=Fd\cos\theta$  

•  $W=Fd\sin\theta$  

•  $W=mg\sin\theta$  

A joule is equivalent to a

• N.

• N $\cdot$ m

• N/m

• kg $\cdot$ $\frac{m}{s^2}$

A parachutist falls at a constant speed for 200m. Which of the following is true?

• The force of gravity is the only force doing work on the parachutist.

• Air resistance is the only force doing work on the parachutist.

• No forces are doing work on the parachutist.

• No net work is done on the parachutist.

Energy that is due to the motion of an object is

• kinetic energy.

• potential energy.

• gravitational potential energy.

• elastic potential energy.

Energy stored due to a gravitational field and a relative height is

• kinetic energy.

• nonmechanical energy.

• gravitational potential energy.

• elastic potential energy.