Chapter 3

Identical cars A and B are traveling down a highway, with A going two times as fast as B. The kinetic energy of A is 1.2 times as large as the kinetic energy of B. 2.4 times as large as the kinetic energy of B. 3.one-half as large as the kinetic energy of B. 4.the same as that of B, because they have the same mass.

2.

Work is done on an object when 1.it moves in a circle with constant speed. 2.it is accelerated in a straight line. 3.it is carried horizontally. 4.All of the above.

2.

Choose the incorrect statement. The total kinetic energy plus potential energy of a body 1.can be negative. always remains 2.constant if the body is falling freely. 3.always remains constant if friction is acting. 4.can remain constant even if the body's speed is decreasing.

3,

A hiker loads camping gear into her SUV. In the process, the rear springs of her vehicle are compressed by a factor of two over their usual length. The potential energy stored in each of the springs under this condition relative to its normal value is 1.half as large. 2.twice as large. 3.one-fourth as large. 4.four times as large.

4.

In an elastic collision between two bodies, which of the following is not true? 1.The total linear momentum of the bodies is the same before and after the collision. 2.The total kinetic energy of the bodies is the same before and after the collision. 3.The total energy (all forms) of the bodies is the same before and after the collision. 4.The two bodies must have equal masses.

4.

The linear momentum of a truck will always be greater than that of a bus if... 1.the truck's mass is larger than the bus's but its speed is the same. 2.the truck's speed is larger than the bus's but its mass is the same. 3.both its mass and its speed are larger than the bus's. 4.Any of the above.

4.any of the above

Identical cars A and B are being driven up the same steep hill. If the power output of A is larger than that of B, what must be happening?

A is going faster

Types of collisions

Elastic collision, inelastic collision

Law of Conservation of Energy

Energy cannot be created or destroyed, only converted from one form to another. The total energy in an isolated system is constant.

Kinetic Energy

Energy resulting from motion. Energy that an object has because it is moving

work =Fd

F=W=mg work=Wd=mgd

In a collision, the total _________ is the same before and after

Linear Momentum

inelastic collision

Momentum befofe= momentum after KE before is not = to KE after

Elastic collision

Momentum before= momentum after KE before= KE after

potential energy-spring

PE=1/2kx^2 d is the change in length, k is the spring constant

potential energy

Scalar, Energy resulting from an object's position or orientation

Work

Scalar, The force that acts times the distance moved in the direction of the force.

Energy

Scalar, The measure of a system's capacity to do work. That which is transferred when work is done

Power

Scalar, The rate of doing work. The rate at which energy is transferred or transformed. Work done divided by the time. Energy transferred divided by the times

Newton's Second Law

Second Law of Motion (alternate form): The net external force acting on an object equals the rate of change of its linear momentum

The use of conservation laws is based on a "before-and-after" approach:

The total amount of the conserved physical quantity before an interaction is equal to the total amount after the interaction.

Law of Conservation of Angular Momentum

The total angular momentum of an isolated system is constant.

The main application of the law of conservation of linear momentum is to collisions.

The total linear momentum before a collision equals the total linear momentum after the collision, if the system is isolated. This applies to all collisions, both elastic and inelastic.

Conservation of Linear Momentum

The total linear momentum of an isolated system is constant.

Conservation laws are powerful tools for analyzing physical systems, particularly those in mechanics.

Their main advantage is that it is not necessary to know the details of what is going on in the system at each instant in time to apply them effectively.

Linear Momentum

Vector, The mass of an object times its velocity. linear momentum = mv

energy

Work always results in a transfer of energy from one thing to another, in a transformation of energy from one form to another, or both.

work

Work is done whenever a force acts through a distance in the same direction as the force. To be able to do work, a device or a person must have energy. The act of doing work involves the transfer of energy from one thing to another, the transformation of energy from one form to another, or both.

The centripetal force acting on a body moving in a circle changes its linear momentum, but it does not change its __________ momentum.

angular

Linear momentum, energy, and angular momentum

are physical quantities that are defined and used mainly because they are conserved in isolated systems.

To be able to do work, a system must have __________.

energy

During a collision between two football players, the total linear momentum of the system cannot be zero

false

The force of gravity cannot do work.

false

The parking brake in most automobiles makes use of a lever so that the force the driver must exert when setting it is reduced. Consequently, the amount of work the driver must do is also reduced.

false

True or False? If both the linear momentum and the kinetic energy of a satellite in orbit around Earth increase, then its angular momentum must also increase.

false

When you lift an object, its gravitational potential energy decreases.

false

Work done inside an isolated system can increase the total energy in the system.

false

Momentum depends on mass and velocity

for different mass objects with the same velocity, momentum is bigger for the larger mass

Diver A jumps off a platform and is going 5 m/s when entering the water. To be going 10 m/s when entering the water, diver B would have to jump off a platform that is _________ times as high as the platform A used.

four

Potential energy increases with

height

Change in momentum is =

impulse

As a baseball player slides into home, the player's kinetic energy is converted into _________ energy.

internal

angular momentum

is a conserved quantity in rotational motion. Just as an applied force is needed to change the linear momentum of a system, an applied torque is required to change the angular momentum of a system. Torque is the analogue of force for angular motion.

Power

is the rate of doing work or using energy. It is the measure of how fast energy is transferred or transformed

In a collision that is inelastic, the total __________ after the collision is not the same as before the collision.

kinetic energy

mechanical energy

kinetic energy, potential energy, and internal energy

for any moving object you can define the

linear mometum

Impulse is equal with change in

momentum

If a force acting on an object and the object's velocity are in opposite directions, the work done by the force is ___________.

negative

As a skier gains speed while gliding down a slope, ____________ energy is being converted into ____________ energy.

potential, kinetic

Law of Conservation of Energy

tells us that in all such conversions, the total amount of energy remains constant.

Torque

torque = change in angular momentum. the net external torque acting on a system equals the rate of change of its angular momentum.

Conservation Laws

total mass in an isolated system is constant

The total linear momentum of the objects in a system before the collision is the same as the total linear momentum after the collision.

total mv before = total mv afte

A conservation law can be used without knowing all of the details about what is occurring inside a system

true

When more people ride upward in an elevator, it requires more power.

true

different forces, different work

work means pushing, pulling, carrying something is not work