homeaccount_circle
PowerComments
parentPhysics
siblingsCalorimetricsCircuitsElectricity and MagnetismFluid DynamicsFluid StaticsFrictionHuman EyeIdeal Gas LawInterference and DiffractionKinematicsMirrors and lensesNewton’s Law of GravitationNewton’s laws of motionOpticsOscillationsPhysics of BreakdancingPolarizationThermal expansionThermodynamic SystemsVectors

Power

Power measures howquickly work gets done. For example, a force of 100J of work in 20 seconds is being done at a rate of 100J/20s = 5J/s. This is the power (P), and from sample calculation above the units are obviously J/s. This is defined as the watt, W, which should not be confused with the W which defines work.

Power = work/time = W/t

The faster work gets done, the greater the power. If there is constant v and force is parallel to path, then P = Fv

Energy is the ability to do work. Moving objects inherently have energy because they can crash into something and exert a force over a distance. Kinetic energy is this energy of motion.

Fd=.5mv2

W=.5mv2

KE = .5mv2

This assumes the initial speed of the object is 0. If it were not, then W = KEfinal - KEinitial.Wtotal = ΔKE.

Â

Potential energy is energy of an object due to position. There is gravitational, electrical, and elastic potential energy. Potential energy is placed on position in a gravitational field. ΔPEgrav=-Wby Fgrav=mgh. If the brick had fallen, it would have been -mgh.

PE = -mgh

Gravity is a conservative force.