AP Physics- Momentum and Energy

What is the unit for all forms of energy?

All forms of energy have units of joules, abbreviated J.

What is the equation for kinetic energy?

Kinetic energy K=1/2mv^2

What is the equation for gravitational potential energy?

Gravitational potential energy Ug=mgh

What is mechanical energy?

The term mechanical energy refers to the sum of a system's kinetic and potential energy.

What is the equation for spring potential energy?

Spring potential energy Us=1/2kx^2 where k is the spring constant, and x is the distance the spring is stretched or compressed from equilibrium.

What is Internal energy?

Internal energy is heat energy that causes an increase in the temperature of the system.

What is the first step to solving work-energy problems?

Define the system.

What is the second step to solve work-energy problems?

Define the two positions you're considering.

What is the third step to solve work-energy problems?

Draw an annotated energy bar chart.

What is the fourth step to solve work-energy problems?

Write an equation where bars + bars = bars.

What direction is positive work?

Positive work is done by a force parallel to an object's displacement.

What direction is negative work?

Negative work is done by a force antiparallel to an object's displacement.

What direction is no work?

No work is done by a force acting perpendicular to the object's displacement.

What direction is work?

Work is a quantity; it does not have a direction but can be positive or negative.

What is the area under a force-displacement graph?

The area under a force vs displacement graph is work.

If an object doesn't move, what is true about work?

If an object doesn't move, no work has been done.

When do you add earth into an energy system?

Add earth if the object changes height.

What is true about object systems?

One object systems only have kinetic energy.

What is true about the distance a string is pulled?

A spring pulls with more force the farther the string is stretched or compressed.

What is the equation for spring force?

The force of a spring is given by the equation F=kx, where k is the spring constant, and x is the distance the spring is stretched or compressed.

What is true about spring constants?

The spring constant of one spring is always the same for the same spring.

What are the standard units of the spring constant?

The standard units of a spring constant are N/m.

What is true when an object is hanging vertically from a spring?

It is easiest to consider a spring-earth-object system.

What is the potential energy of a spring-earth-object system?

The potential energy of a spring-earth-object system is PE=1/2kx,^2 where x is measured from the position where the object would hang in equilibrium.

What is the definition of power?

Power is defined as the amount of work done in one second, or energy used in one second.

What is the equation for power?

Power = Work/time

What are the units of power?

The units of power are joules per second, also known as watts.

What is the alternate way of calculating power?

The alternate way of calculating power when a constant force acts is power = force * (average) velocity.

What is true about mechanical energy in an elastic collision?

In an elastic collision, the mechanical energy of the system is conserved.

What is true about objects that stick together and elastic collisions?

Collisions for which objects stick together can not be elastic.

What is true about objects that bounce apart and elastic collisions?

Collisions for which objects bounce off each other may or may not be elastic.

What is the equation for momentum?

Momentum is equal to mass times velocity: p=mv

What are the standard units of momentum?

The standard untits of momentum are newtonsseconds, abbriviated Ns (equilivant to kg*m/s)

What direction is an object's momentum?

An object's momentum is in the same direction as its motion.

What is true about a system of objects with no external forces?

When no external forces act on a system of objects, the system's momentum can not change.

What is true about the momentum of two objects before a collision?

The total momentum of two objects before a collision is equal to the total momentum of the objects after the collision.

What is true about the momentum of two objects in a system when they are moving in the same direction?

Because they are vectors, when they move in the same direction, they add.

What is true about the momentum of two objects in a system when they are moving in opposite directions?

Because they are vectors, when they move in the opposite direction, they subtract.

What is true about a system's center of mass?

A system's center of mass obeys Newtons seconds law: the velocity of the center of mass only changes when an external net force acts on the system.

What is the first way impulse can be determined?

Impulse can be determined by the change in an object's momentum.

What is the second way impulse can be determined?

Impulse can be determined by the force experienced multiplied by the time interval of the collision, J=Ft.

What are the units for impulse?

Impulse has the same units as momentum, N*s

On a force-time graph, what is the area under the graph?

The area under a force-time graph is impulse.

What is the slope of a momentum time graph?

The slope of a momentum time graph is the net force.

What does the momentum form of the N2L state?

The momentum form of N2L states that Fnet=impulse/change in time.

What is delta P?

Delta P is the change in momentum.

When there are no external forces, what is delta p?

When there are no external forces, delta p = 0