Physics Definitions (Appendix 3)

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Listed below are definitions of some of the more important physics quantities. Each quantity is defined in words and then the defining equation is given, using standard notation. Quantities which are vectors are shown with their symbol underlined. When vectors are multiplied the equations use a raised dot for the dot or scalar product and a X for the cross or vector product.

Velocity: change in position/time interval

V = ΔX/Δt

Acceleration: change in velocity/time interval

a = ΔV /Δt

Impulse:force X time

impulse = FΔt

Momentum: mass X velocity

p = mV

Torque: radius arm X force (perpendicular)

Τ = R X F

Angular momentum: momentum X radius (circular path only)

angular momentum = m(V X R)

Work: force times distance moved in the direction of the force

W = F ΔX

Power: work/time interval

P = W/Δt

Current: charge passing/time

I = q/Δt

Potential difference: diff in electric PE/unit charge

V = ΔPE/Δq

Gravitational field: force/mass

gravitational field = F/m

Electric field: force/charge

E = F/q

Magnetic field: *force/(current X length)

B = F/IL

Wavelength: distance between corresponding parts of a wave

Frequency: number of cycles per time

f = #/ t

Period: time per cycle

T = 1/f

Coefficient of friction: friction force/normal force

μ = F_f/F_N

* NOTE: Since vector division is not defined the equation for magnetic field is not really correct. As it stands it would only apply if the current were perpendicular to the magnetic field. The correct way of writing the equation is to give the force in terms of the magnetic field and the current as follows:

F = I(L X B)

where L is the length of wire with its direction being the direction of the positive current in the wire.