Chapter 3 Energy

The smallest part of the total energy of the ball of Multiple Choice 30 is a.kinetic energy b.potential energy relative to the ground c.rest energy d.momentum

a.kinetic energy

Which of the following is not a unit of work? a.newton-meter b.joule c.kilogram-meter d.watt-hour

c.kilogram-meter

The work done in holding a 50-kg object at a height of 2 m above the floor for 10 s is a.0 b.250 J c.1000 J d.98,000 J

a. 0

A 1-kg object has a potential energy of 1 J relative to the ground when it is at a height of a.0.102 m b.1 m c.9.8 m d.98 m

a.0.102 m

A 10,000-kg freight car moving at 2 m/s collides with a stationary 15,000-kg freight car. The two cars couple together and move off at a.0.8 m/s b.1 m/s c.1.3 m/s d.2 m/s

a.0.8 m/s

An object has a rest energy of 1 J when its mass is a.1.1 × 10−17 kg b.3.3 × 10−9 kg c.1 kg d.9 × 1016 kg

a.1.1 × 10−17 kg

A total of 4900 J is used to lift a 50-kg mass. The mass is raised to a height of a.10 m b.98 m c.960 m d.245 km

a.10 m

The lightest particle in an atom is an electron, whose rest mass is 9.1 × 10−31 kg. The energy equivalent of this mass is approximately a.10−13 J b.10−15 J c.3 × 10−23 J d.10−47 J

a.10−13 J

A bomb dropped from an airplane explodes in midair. a.Its total kinetic energy increases. b.Its total kinetic energy decreases. c.Its total momentum increases. d.Its total momentum decreases.

a.Its total kinetic energy increases.

The total amount of energy (including the rest energy of matter) in the universe a.cannot change b.can increase but not decrease c.can decrease but not increase d.can either increase or decrease

a.cannot change

A spacecraft has left the earth and is moving toward Mars. An observer on the earth finds that, relative to measurements made when the spacecraft was at rest, its a.length is shorter b.KE is less than 1/2 mv2 c.clocks tick faster d.rest energy is greater

a.length is shorter

When the momentum of a moving object is increased, there must also be an increase in which one or more of the following of the object's properties? a.speed b.acceleration c.kinetic energy d.potential energy

a.speed c.kinetic energy

The highest MA that can be obtained by a system of two pulleys is a.2 b.3 c.4 d.5

b.3

A 40-kg boy runs up a flight of stairs 4 m high in 4 s. His power output is a.160 W b.392 W c.40 W d.1568 W

b.392 W

A 150-kg yak has an average power output of 120 W. The yak can climb a mountain 1.2 km high in a.25 min b.4.1 h c.13.3 h d.14.7 h

b.4.1 h

A moving object must have which one or more of the following? a.potential energy b.kinetic energy c.rest energy d.momentum

b.kinetic energy c.rest energy d.momentum

Albert Einstein did not discover that a.the length of a moving object is less than its length at rest b.the acceleration of gravity g is a universal constant c.light is affected by gravity d.gravity is a warping of spacetime

b.the acceleration of gravity g is a universal constant

A 30-kg girl and a 25-kg boy are standing on frictionless roller skates. The girl pushes the boy, who moves off at 1.0 m/s. The girl's speed is a.0.45 m/s b.0.55 m/s c.0.83 m/s d.1.2 m/s

c.0.83 m/s

A machine has a MA of 6.0. The work input needed by the machine to raise a 40-kg load by 3.0 m is a.0.12 kJ b.0.20 kJ c.1.2 kJ d.7.1 kJ

c.1.2 kJ

A 1-kg object has kinetic energy of 1 J when its speed is a.0.45 m/s b.1 m/s c.1.4 m/s d.4.4 m/s

c.1.4 m/s

A person uses a force of 300 N to pry up one end of a 120-kg box using a lever 2.4 m long. The distance from the end of the box to the fulcrum is a.40 cm b.49 cm c.81 cm d.171 cm

c.81 cm

A spinning skater whose arms are at her sides then stretches out her arms horizontally. a.She continues to spin at the same rate b.She spins more rapidly c.She spins more slowly d.Any of the choices could be correct, depending on how heavy her arms are

c.She spins more slowly

The operation of a rocket is based upon a.pushing against its launching pad b.pushing against the air c.conservation of linear momentum d.conservation of angular momentum

c.conservation of linear momentum

The formula 1/2 mv2 for kinetic energy a.is the correct formula if v is properly interpreted b.always gives too high a value c.is the low-speed approximation to the correct formula d.is the high-speed approximation of the correct formula

c.is the low-speed approximation to the correct formula

A 1-kg ball is thrown in the air. When it is 10 m above the ground, its speed is 3 m/s. At this time most of the ball's total energy is in the form of a.kinetic energy b.potential energy relative to the ground c.rest energy d.momentum

c.rest energy

Car A has a mass of 1000 kg and is moving at 60 km/h. Car B has a mass of 2000 kg and is moving at 30 km/h. The kinetic energy of car A is a.half that of car B b.equal to that of car B c.twice that of car B d.4 times that of car B

c.twice that of car B

The 2-kg blade of an ax is moving at 60 m/s when it strikes a log. If the blade penetrates 2 cm into the log as its KE is turned into work, the average force it exerts is a.3 kN b.90 kN c.72 kN d.180 kN

d.180 kN

The work done in lifting 30 kg of bricks to a height of 20 m is a.61 J b.600 J c.2940 J d.5880 J

d.5880 J

The work a 300-W electric grinder can do in 5.0 min is a.1 kJ b.1.5 kJ c.25 kJ d.90 kJ

d.90 kJ

Two balls, one of mass 5 kg and the other of mass 10 kg, are dropped simultaneously from a window. When they are 1 m above the ground, the balls have the same a.kinetic energy b.potential energy c.omentum d.acceleration

d.acceleration

According to the principle of relativity, the laws of physics are the same in all frames of reference a.at rest with respect to one another b.moving toward or away from one another at constant velocity c.moving parallel to one another at constant velocity d.all of these

d.all of these

The upper limit to the speed of an object with mass a.depends on the mass b.corresponds to a KE equal to its rest energy c.is the speed of sound d.is the speed of light

d.is the speed of light

When the speed of a moving object is halved, a.its KE is halved b.its PE is halved c.its rest energy is halved d.its momentum is halved

d.its momentum is halved

It is not true that a.light is affected by gravity b.the mass of a moving object depends upon its speed c.the maximum speed anything can have is the speed of light d.momentum is a form of energy

d.momentum is a form of energy

An object at rest may have a.velocity b.momentum c.kinetic energy d.potential energy

d.potential energy