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Gravity definition
A field that exists between any two objects with mass.

Field definition
An invisible influence that can exert a force on a mass or charge.

Universal Law of Gravitation (force due to gravity)
(In space)
F = mg
(Near earth)

Formula for gravity, strength of gravitational field, acceleration due to gravity

Gravitational Potential Energy
(In space)
PE = mgh
(Near earth)

Friction facts
 Friction opposes sliding not motion.
 If there is sliding, it's kinetic friction; if there's no sliding, it's static friction.
 Static µ is always greater than kinetic µ.
 Surface area does not increase friction when the mass is the same.

Force due to friction formula
F _{f} = µ _{(s/k)}F _{N}
F _{f} = µ _{(s/k)}mgcos

Force down an inclined plane formula
F = mgsin

Normal force on an inclined plane formula
F _{N} = mgcos

Velocity at the base of an inclined plane
V_{f} = √(2gh)

Hooke's Law
F = k∆x
 x  displacement
 k  spring constant

Elastic Potential Energy formula

Simple Harmonic Motion formulas
T = 2π√(m/k)
(mass on a spring)
T = 2π√(L/g)
(pendulum)
 T  period (time/wave)
 m  mass
 k  spring constant
 L  length of pendulum
 g  gravity

Equililbrium terms
 Terminal velocity
 Constant velocity
 Objects at rest
 Balanced fulcrums or boards on strings
 Objects floating in liquid


Solving for systems in and not in equilibrium
Equilibrium  list all the forces and put them equal to one another.
Not Equilibrium  list all the forces and add "ma" to the loosing side.


Centripetal vs. Centrifugal
If a string is pulling a ball into a circular motion, the string's force on the ball is centripetal and the ball's force on the string is centrifugal.
Centrifugal does not exist.


Rotational equilibrium
 An object is in rotational equilibrium if:
 1. It is NOT rotataing
 2. It is rotating with a constant angular velocity/frequency

Momentum
momentum is inertia increased by velocity and is always conserved (remains constant) in an isolated system.

Impulse
 Impulse = ∆
 Impulse = m∆v
 Impulse = F_{avg}t
 If there is no change in velocity, there can be no impulse.
 The greater the change in velocity the greater the change in impulse.

Elastic Collisions
 (KE_{1} + KE_{2})_{before} + (KE_{1} + KE_{2})_{after}
 In elastic collisions momentum and energy are both conserved.

Inelastic Collisions
m_{1}v_{1} + m_{2}v_{2} = m_{1}v_{1} + m_{2}v_{2 }
In inelastic collisions momentum is conserved but energy is not. For perfectly inelastic collisions the equations becomes:
m_{1}v_{1} + m_{2}v_{2} = (m_{1} + m_{2})v_{3}


Strain
∆dimension/original dimension

Modulus of elasticity (ME)
stress/strain
 Young's modulus  simultaneous pushing or pulling, perfectly lined up with one another.
 Shear modulus  simultaneous pushing or pulling not perfectly lined up.
 Bulk modulus  simultaneous compression from all sides.

Thermal expansion formula
∆L = L _{o}∆T
 T  temperature
 L  length in inches
  coefficient of thermal expansion

Internal energy
The energy of internal vibrations of molecules or atoms within a system.

Heat energy
Energy dissipated as heat. On the MCAT this usually means heat dissipated from a collision.
Heat energy and internal energy are almost synonymous.

Chemical energy
The energy contained within chemical bonds, or the energy stored/released due to the separation and/or flow of electrons.

Mechanical energy
ME = KE + PE

Work formulas
 W = ∆Energy
 W = Fdcos
Units  Joules ( ) or ( )

