Energy and Momentum

Work

-Energy transferred to an object when a force acting on the object moves a distance

-must be parallel to displacement

Positive work

Force and distance are in the same direction

Negative work

Force and distance are in opposite direction

Zero work

Force or displacement are zero, force and displacement are perpendicular

Work energy theorem

Total work done on an object equals the change in the object’s kinetic energy, provided there is no change in other forms of energy

Kinetic energy

Energy of an object in motion

Law of conservation of energy

For an isolated system, energy can be converted into different forms, but never created or destroyed

Closed system

system that doesn’t lose or gain energy

Open system

System that exchanges energy with its surroundings

Total mechanic energy

Sum of kinetic, gravitional potential, and elastic potential energy

Thermal energy

The internal energy associated with motion of atoms and molecules

Hooke’s Law

Magnitude of force exterted by a spring is directly proportional from the distance the spring has moved from rest

Simple harmonic motion

Back and forth motion that would occur if no friction were present

Thermal energy

Energy associated with motion of atoms and molecules

Force constant, K

How strong a spring in

Ideal spring

No friction in a spring

Elastic potential energy

Energy stored in an object through stretching, compressing, and Torsion

Damping

Friction on SHM

Over damped

Return to rest slowly

Under damped

Go back and forth slower and slower until at rest

Critically damped

Go back to rest quickly

Perpetual motion machine

Machine that can operate forever without restarting

Gravitational potential energy

Energy due to elevation above a reference point

Elastic collision

Kinetic energy and momentum are conserved

Inelastic collision

Momentum is conserved, energy is not

Completely inelastic

Objects stick together after collision

When is momentum not conserved

When there is no external force acting on the object

Linear momentum

Momentum in a straight line

Impulse

Change in momentum