Physics chapter 5

In which of the following situations is mechanical energy most likely to be conserved? A A football flies through the air. B A feather falls from the sky. C A skateboard rolls into the grass. D A hockey player digs his skates into the ice.

A A football flies through the air.

A painter lifts a bucket of paint, carries it 5 m horizontally, then sets it back down. Which of the following is true? A The force of gravity does negative work when the worker lifts the bucket. B The painter does positive work on the bucket when carrying it horizontally at constant speed. C The painter does positive work on the bucket when setting it down. D No net work is done on the bucket.

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

Energy that is due to the motion of an object is A kinetic energy. B potential energy. C gravitational potential energy. D elastic potential energy.

A kinetic energy.

If a machine increases the distance over which work is done, A the force required to do the work is less. B the force required to do the work is greater. C the force required to do the work is the same. D the amount of work done is increased.

A the force required to do the work is less.

In which of the following cases is no work done? A A weightlifter lifts a barbell. B A weightlifter holds a barbell overhead. C A weightlifter slowly lowers a barbell. D A weightlifter drops a barbell and the barbell falls to the ground.

B A weightlifter holds a barbell overhead.

A joule is equivalent to a A N. B N•m. C N/m. D kg •m/s2.

B N•m.

Friction does -400 J of net work on a moving car. How does this affect the kinetic energy of the car? A The kinetic energy increases by 400 J. B The kinetic energy decreases by 400 J. C The kinetic energy decreases by 160 kJ. D The kinetic energy does not change.

B The kinetic energy decreases by 400 J.

Which equation is used to calculate the work done on an object by a force at an angle, , to the displacement? A W = Fd B W = Fdcos C W = Fdsin D W = mgsin

B W = Fdcos

Which of the following is not a form of mechanical energy? A kinetic energy B chemical potential energy C gravitational potential energy D elastic potential energy

B chemical potential energy

If a machine decreases the distance over which work is done, A the force the machine applies is less. B the force the machine applies is greater. C the force the machine applies is the same. D the amount of work done is decreased.

B the force the machine applies is greater.

The work-kinetic energy theorem states that A the net work done on an object equals the kinetic energy of the object. B the net work done on an object equals the change in the kinetic energy of the object. C the change in the net work done on an object equals the kinetic energy of the object. D the change in the net work done on an object equals the change in the kinetic energy of the object.

B the net work done on an object equals the change in the kinetic energy of the object.

An egg suspended above the ground has 2.0 J of gravitational potential energy. The egg is then dropped and falls to the ground. What is the kinetic energy of the egg just as it reaches the ground? A -2.0 J B 0 J C 2.0 J D 4.0 J

C 2.0 J

How much work can a motor with a power output of 25 W do in 1 s? A 1/25 J B 1 J C 25 J D 25 W

C 25 J

Which of the following is not a valid equation for power? A P = w/tΔ B P = Fd/Δt C P = Fv/Δt D P = Fv

C P = Fv/Δt

How does the elastic potential energy in a mass-spring system change if the displacement of the mass is doubled? A The elastic potential energy decreases to half its original value. B The elastic potential energy doubles. C The elastic potential energy increases or decreases by a factor of 4. D The elastic potential energy does not change.

C The elastic potential energy increases or decreases by a factor of 4.

How does the kinetic energy of an object change if the object's speed doubles? A The kinetic energy decreases to half its original value. B The kinetic energy doubles. C The kinetic energy increases by a factor of 4. D The kinetic energy does not change.

C The kinetic energy increases by a factor of 4.

The SI unit for power is A N•m. B J. C W. D hp.

C W.

Energy stored in the gravitational field of interacting bodies is A kinetic energy. B nonmechanical energy. C gravitational potential energy. D elastic potential energy.

C gravitational potential energy.

If the sign of work is negative, A the force is in the same direction as the displacement. B the force is perpendicular to the displacement. C the component of the force that does work is in the direction opposite the displacement. D the component of the force that does work is perpendicular to the displacement.

C the component of the force that does work is in the direction opposite the displacement.

The mechanical energy of a system of objects is A the sum of kinetic energy and gravitational potential energy. B the sum of kinetic energy and elastic potential energy. C the sum of kinetic energy and all relevant forms of potential energy. D the sum of all forms of energy.

C the sum of kinetic energy and all relevant forms of potential energy.

Work is done on an object A whenever a force acts on the object. B whenever a force is perpendicular to the displacement of the object. C whenever a force causes a displacement of the object. D whenever a net force acts on the object.

C whenever a force causes a displacement of the object.

Which of the following sentences uses work in the scientific sense. A Stan goes to work on the bus. B Anne did work on the project for 5 hours. C Joseph found that holding the banner in place was hard work. D An engine does work on a car when the car is moving.

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

A parachutist falls at a constant speed for 200 m. Which of the following is true? A The force of gravity is the only force doing work on the parachutist. B Air resistance is the only force doing work on the parachutist. C No forces are doing work on the parachutist. D No net work is done on the parachutist.

D No net work is done on the parachutist.

Which of the following is true of the conservation of energy in a closed system? A Kinetic energy is always conserved. B Potential energy is always conserved. C Mechanical energy is always conserved. D Total energy is always conserved.

D Total energy is always conserved.

If mechanical energy is conserved in a system, the energy at any point in time can be in the form of A kinetic energy. B gravitational potential energy. C elastic potential energy. D all of the above

D all of the above

Which of the following is evidence that frictional forces are present in a system? A Interactions in the system cause an increase in temperature. B Interactions in the system produce sound. C Mechanical energy is not conserved. D all of the above

D all of the above

Which of the following does not affect gravitational potential energy? A an object's mass B an object's height relative to a zero level C the free-fall acceleration D an object's speed

D an object's speed

A 100 W light bulb A converts 100 J of kinetic energy to potential energy each second. B converts 100 J of potential energy to kinetic energy each second. C converts 100 J of mechanical energy to nonmechanical energy each second. D converts 100 J of electrical energy to other forms of energy each second.

D converts 100 J of electrical energy to other forms of energy each second.

Energy associated with a compressed or stretched object is A kinetic energy. B potential energy. C gravitational potential energy. D elastic potential energy.

D elastic potential energy.

Mechanical energy is not conserved when A gravitational potential energy is converted to kinetic energy. B kinetic energy is converted to gravitational potential energy. C kinetic energy is converted to elastic potential energy. D friction is not negligible.

D friction is not negligible.

Which of the following refers to the rate at which energy is transferred? A work B kinetic energy C mechanical energy D power

D power

Which of the following refers to the rate at which work is done? A energy B kinetic energy C mechanical energy D power

D power