Chapter 4 Work and Energy

In which one of the following situations is zero net work done?

• A ball rolls down an inclined plane.

• A physics student stretches a spring.

• A projectile fall towards the surface of Earth.

• A box is pulled across a rough floor at constant velocity.

A ball is thrown directly upward. Which of the following is TRUE before it reaches its maximum height?

• A. Its potential energy increases and kinetic energy decreases.

• Its potential energy always equals to kinetic energy.

• Its potential energy decreases and kinetic energy increases.

• Its potential energy is 0 J and kinetic energy is constant.

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Which one of the following situations will there be an increase in the kinetic energy?

• A stone is thrown upward until it reaches maximum height.

• A ball starts from rest and freely rolls downhill.

• A box is pulled across a rough floor at constant speed.

• A satellite travels in a circular orbit around the Earth at fixed altitude.

Which one of the following systems is there a decrease in gravitational potential energy?

• A boy stretches a horizontal spring.

• A girl jumps down from a bed.

• A crate rests at bottom of an inclined plane.

• A car ascends a steep hill.

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1 Joule can be defined as work done by

• A force of 1 N which results in a displacement of 1 m in the direction of force.

• A force of 1 N which results in a displacement of 1 cm in the direction of force.

• A force of 1 N which results in a displacement of 10 m in the direction of force.

• A force of 1 N which results in a displacement of 1 km in the direction of force.

When a body slides against a rough horizontal surface, the work done by friction is

• Positive.

• Zero.

• Negative.

• Constant.

In force against displacement graph, the area under the graph represents

• Velocity.

• Acceleration.

• Force.

• Work done.

A car accelerates uniformly from rest. When does the car require the greatest power?

• When the car first accelerates from rest.

• Just as the car reaches its maximum speed

• The question is misleading because the power required is constant.

• When the car reaches half its maximum speed

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If the speed of a particle is doubled, what happens to

its kinetic energy?

• It becomes four times larger.

• It becomes two times larger.

• It becomes half

• It is unchanged.

A block of mass m is dropped from the fourth floor of an office building, subsequently hitting the sidewalk at speed v. From what floor should the mass be dropped to double that impact speed?

• the eighth floor

• the tenth floor

• the twelfth floor

• the sixteenth floor

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