(Multiple choice)

(1) True or false: 

(a) Only the net force acting on an object can do work. 

(b) No work is done on a particle that remains at rest. 

(c) A force that is always perpendicular to the velocity of a particle never does work on the particle.

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(2)

An object initially has kinetic energy K. The object then moves in the opposite direction with three times it s initial speed. What is the kinetic energy now? 

(a) K

(b) 3K 

(c) -3K 

(d) 9K 

(e) -9K

(3)

The dimension of power is _______. 

(a) [M] * [L]² * [T]² 

(b) [M] * [L]² / [T] 

(c) [M] * [L]² / [T]² 

(d) [M] * [L]² / [T]³

(4) True or false:

A kilowatt-hour is a unit of power.

(5)

The engine of a car operates at constant power. The ratio of acceleration of the car at a speed of 60 km/h to that at 30 km/h (neglecting air resistance) is

(a) 1/2

(b) 1/√2

(c) √2

(d) 2

(6)

A car starts from rest and travels at constant acceleration. Which of the following statements are true? 

(a) The power delivered by the engine is constant. 

(b) The power delivered by the engine increases as the car gains speed. 

(c) The power delivered by the engine decreases as the car gains speed. 

(d) Both (b) and (c) are correct.

(7)

Two knowledge seekers decide to ascend a mountain. Sal chooses a short, steep trail, while Joe, who weighs the same as Sal, goes up via a long, gently sloped trail. At the top, they get into an argument about who gained more potential energy. Which of the following is true. 

(a) Sal gains more gravitational potential energy than Joe. 

(b) Sal gains less gravitational potential energy than Joe. 

(c) Sal gains the same gravitational potential energy as Joe. 

(d) To compare energies, we must know the height of the mountain. 

(e) To compare energies, we must know the length of the two trails.

(8)

The gravitational potential energy of an object changes by − 6 J. It follows that the work done by the gravitational force on this object is 

(a) −6 J and the elevation of the object is increased. 

(b) −6 J and the elevation of the object is decreased. 

(c) +6 J and the elevation of the object is increased. 

(d) +6 J and the elevation of the object is decreased.