Exam 3 ch 4

If you exert 1 N for a distance of 1 m in 1 s, you will deliver a power of

1 W.

A 1-kg glider and a 2-kg glider both slide toward each other at 1 m/s on an air track. They collide and stick. The combined mass moves at

1/3 m/s.

Consider massive gliders that slide friction-free along a horizontal air track. Glider A has a mass of 1 kg, a speed of 1 m/s, and collides with glider B, which has a mass of 5 kg and is at rest. If they stick upon collision, their speed after collision will be

1/6 m/s.

A ball is moving at 4 m/s and has a momentum of 48 kg×m/s. What is the ball's mass?

12 kg

Exert 100J in 50s, and your power output is

2 W

A 2-kg mass has 40 J of potential energy with respect to the ground. Approximately how far is it located above the ground?

2 m

How many joules of energy are in 1 kWh?

3.6 MJ

A bow is drawn so that it has 40 J of potential energy. When fired, the arrow will ideally have a kinetic energy of

40 J.

In a simple machine, how much work is done when an input of 10 N acts over a distance of 5 m?

50 J.

A 2-kg mass is held 4 m above the ground. What is the approximate potential energy of the mass with respect to the ground?

80 J

How does impulse differ from force?

Force is a push or pull, while impulse is the product of force and time.

In what unit POWER is measured?

In Watt

What is the law of energy conservation?

In the absence of external work input or output, the energy of a system remains unchanged. Energy cannot be created or destroyed.

What does it mean to say that a quantity is conserved?

It means that the quantity remains unchanged in a process.

Which has a greater momentum − a heavy truck at rest or a moving skateboard?

Moving skateboard.

The conservation of momentum is most closely related to

Newton's Third Law.

Is it possible to design a machine that has an efficiency greater than 100%?

No because a machine that has an efficiency greater than 100% outputs more energy than it uses, therefore, the machine creates additional energy. It violates the law of energy conservation.

Can you produce a net impulse on a car by sitting inside and pushing on the dashboard?

No, because your push is internal. To change the automobile's momentum, an external force must be applied

Consider a baseball that is caught and thrown at the same speed. Which case illustrates the greatest change in momentum?

The baseball being caught and then thrown back.

Consider a baseball that is caught and thrown at the same speed. Which case requires the greatest impulse?

The baseball being caught and then thrown back.

For the same force, which cannon imparts the greater speed to a cannonball − a long cannon or a short one?

The long cannon.

When one does twice the work in twice the time, the power expended is

The same

How can a huge ship have an enormous momentum when it moves relatively slowly?

The ship has enormous momentum due to huge mass.

What is the source of energy that powers a hydroelectric power plant?

The sunlight that evaporated water that eventually falls as rain and fills the reservoir.

True or false: One watt is the unit of power equivalent to 1 joule per second.

True

What is (are) the way(s) in which the impulse exerted on something can be increased?

Two ways to increase impulse are to increase force or increase the time the force is exerted.

In what units are work and energy measured?

Work and energy are measured in joules.

Which of the following has the largest momentum relative to the earth?

a pickup truck speeding along a highway

Momentum is conserved in

all collisions in which external forces don't affect motion.

A hydraulic press, like a simple level, properly arranged is capable of multiplying energy input.

always false

When you are traveling twice as fast your kinetic energy is increased

by four.

A cannon recoils from firing a cannonball. The speed of the cannon's recoil is small because the

cannon has more mass than the ball.

An open freight car rolls friction-free along a horizontal track in a pouring rain that falls vertically. As water accumulates in the car, its speed

decreases.

Energy cannot be

destroyed.

In bungee jumping, the change in a jumper's kinetic energy equals the average force of the bungee cord multiplied by the stretching

distance.

A freight train rolls along a track with considerable momentum. If it rolls at the same speed but has twice as much mass, its momentum is

doubled.

A boxer rides with the punch so as to reduce

force

The work that is done when twice the load is lifted twice the distance is

four times as much.

Momentum is transferred to the ground when an apple falls on it. The momentum absorbed by the ground is

greater than that of the apple only if the apple bounces.

Compared to a recoiling rifle, the bullet fired has a greater

kinetic energy.

A slowly moving ship has a large momentum because of its

large mass.

What does an object have when moving that it doesn't have when at rest?

momentum

Two objects, A and B, have the same size and shape, but A is twice as heavy as B. When they are dropped simultaneously from a tower, they reach the ground at the same time, but A has greater

momentum.

When an increase in speed doubles the momentum of a moving body, its kinetic energy.

more than doubles

When an increasing in speed doubles the momentum of moving body, its kinetic energy

more than doubles

If you push for an hour against a stationary wall, no work is done

on the wall.

The quantity called impulse can be measured by

the product of force and time.

Two identical arrows, one with twice the kinetic energy of the other, are fired into a hay bale. The faster arrow will penetrate

twice as far as the slower arrow.

You lift a barbell a certain distance from the floor. If you lift it twice as high, its potential energy is

twice as great

When you lift a load twice as high, the increase in potential energy is

twice as much

An object is raised above the ground gaining a certain amount of potential energy. If the same object is raised twice as high, it gains

twice as much potential energy.

A 1000-kg car and a 2000-kg car are hoisted the same distance in a gas station. Raising the more massive car requires

twice as much work.

If you push an object twice as far while applying the same force, you do

twice as much work.

When an object is lifted 10 m, it gains a certain amount of potential energy. If the same object is lifted 20 m, its potential energy gain is

twice as much.

Recoil is noticeable if we throw a heavy ball while standing on roller skates. If instead we go through the motions of throwing the ball but hold onto it, our net recoil will be

zero.