Physics Ch 2

Power (P)

Rate of energy transfer

dynamic equilibrium

all velocities are constant

Static equilibrium

all velocities are zero equilibrium

Torque

is a measure of a force's ability to cause rotational acceleration

Ramp

is an inclined plane that reduces the force needed to do work by increasing the distance over which the force is applied.

Heat (q)

is energy that is transferred between a system and its surroundings due to a temperature difference between them.

Work (W)

is energy transferred for any reason other than a temperature difference. Thus all work is energy transfer, but not all energy transfer is work. By 'transfer' we mean transfer from the system to the surroundings or vice versa. The energy transferred out of a system equals the energy transferred into its surroundings, and the energy transferred into a system equals the energy transferred out of its surroundings.

Gravitational potential energy

is potential energy created by the force ofgravity. Gravitational potential energy between any two masses is given by Ug =- Gm1m2/r, where C is the universal gravitational constant, m1 and m2 are the two masses, and r is the distance between their centers of gravity. The negative sign indicates that energy decreases as the distance between objects decreases.

Machines

reduce the force required to do a given amount of work

Static and dynamic equilibrium are both defined by constant velocity. The only difference is that in static equilibrium, the constant velocity is zero. Problems involving static or dynamic equilibrium are solved in exactly the same way.

For a system not in equilibrium, the sum of the forces equals the mass of the system multiplied by the acceleration of the system, or F = ma.

Joule (J)

One Joule is 1 k g m2 /s2 , which is the same as 1 Nm.

If a system is not in equilibrium, its center of mass is accelerating translationally or its parts are accelerating rotationally.

The MCAT® does not test angular acceleration, where parts are accelerating rotationally, so a system not in equilibrium on the MCAT® must have only translational acceleration.

Terminal Velocity

where the gravitational force downward is equal to the force ofair resistance upward. At this point, he is in equilibrium and his acceleration is zero.