chapter 3 physics final

Linear momentum

Mass multiplied by velocity. It describes an object's motion.

Is momentum a scalar or vector

Vector. It has both magnitude and direction.

SI unit of momentum

$$kg\cdot m/s$$

Momentum of a stationary object

Zero.

Effect of speed on momentum

The faster it moves, the greater its momentum.

Heavy vs. light object at the same speed

The heavier object.

Newton's Second Law (momentum form)

Net external force equals the rate of change of an object's momentum.

Impulse

The effect of a force acting over a period of time that changes an object's momentum.

Law of conservation of linear momentum

The total linear momentum of an isolated system remains constant.

Isolated system

A system with no outside forces causing changes in the momentum of the objects inside it.

Momentum in a collision

Total momentum before the collision equals total momentum after the collision.

Momentum conservation equation for a collision

Total $mv$ before = total $mv$ after.

Billiard ball collision

One ball loses momentum while the other gains momentum, but the total momentum stays the same.

Ice skater throwing an object

The skater moves backward with momentum equal in magnitude to the object's forward momentum.

Rocket propulsion

They eject exhaust gases backward, gaining momentum in the forward direction.

Energy

The measure of a system's capacity to do work.

SI unit of energy

Joule (J).

Energy as a scalar or vector

Scalar. It has no direction.

Mechanical energy

Energy associated with the motion and position of objects.

Two main forms of mechanical energy

Kinetic energy and potential energy.

Kinetic energy

Energy an object has because it is moving.

Potential energy

Energy an object has because of its position or orientation.

Translational kinetic energy

Energy an object possesses because it moves from one position to another.

Kinetic energy of a spinning object

Its mass, rotation rate, and how its mass is distributed.

Relative kinetic energy

Speed depends on the observer's frame of reference.

Gravitational potential energy

Energy an object has because of its height or position in a gravitational field.

Relative gravitational potential energy

Height can be measured from different reference levels.

Negative potential energy

Yes. It is negative if the object is below the chosen reference level.

Can potential energy be negative?

Energy stored in objects such as springs and rubber bands when they are stretched or compressed.

Internal energy

The total energy of all the atoms and molecules within a substance.

Conversion of kinetic energy to internal energy

Through processes such as friction or impact.

Work

The process of transferring energy from one object or system to another.

Work formula

$W = Fd$, where W is work, F is force, and d is distance moved in the direction of the force.

SI unit of work

Joule (J).

Positive work

Work is positive when force and displacement are in the same direction.

Negative work

Work is negative when force and displacement are in opposite directions.

Zero work

When the force is perpendicular to the object's displacement or has no component in the direction of motion.

Carrying a box horizontally at constant height

The upward force supporting the box is perpendicular to its horizontal displacement.

String force in uniform circular motion

The string's force points toward the center, perpendicular to the object's motion.

Crowbar advantage

It allows the same amount of work to be done using a smaller applied force.

Law of conservation of energy

Energy cannot be created or destroyed; it can only be converted from one form to another.

Total energy in an isolated system

It remains constant.

Falling object energy conversion

Gravitational potential energy converts into kinetic energy.

Speed of a freely falling object

No. It depends on how far the object has fallen and the acceleration due to gravity.

Energy in a swinging spring or bouncing system

Potential energy and kinetic energy continually convert into one another.

Energy conversions in a wind generator

Wind's kinetic energy converts into electrical energy, with some internal energy also produced through friction.

Elastic collision

A collision in which total kinetic energy after the collision equals total kinetic energy before it.

Inelastic collision

A collision in which total kinetic energy after the collision is not equal to the total kinetic energy before it.

Carts colliding and bouncing apart elastically

Total kinetic energy remains the same.

Carts sticking together after colliding

They undergo an inelastic collision.

Increase in kinetic energy after a collision

Yes. Stored potential energy can convert into kinetic energy during a collision.

Non-contact collision

A collision or interaction in which objects affect one another without physically touching, such as gravitational interactions.

Power

The rate at which work is done or energy is transferred.

SI unit of power

Watt (W).

One watt

One joule of energy transferred per second.

Greater power for the same work

The machine that completes the work in less time.

Law of conservation of angular momentum

The total angular momentum of an isolated system remains constant.

Angular speed when radius decreases with conserved angular momentum

Angular speed increases.

Torque

The turning effect of a force around an axis.

Doubling the lever arm with the same force

Torque doubles.

Positive torque

Counterclockwise rotation.

Negative torque

Clockwise rotation.