Formulas for Test 4

Test 4 will cover homeworks 16 to 21 (i.e. Chaps. 22, 23, 24, 25, 26, 28, 29)

Speed or velocity = change in distance/change in time, v = d/t [Units: m/s]

Acceleration = change in velocity/change in time, a = (vf - vi)/t [Units: m/s/s or m/s2]


For acceleration under gravity (starting from rest at time t = 0s): g = 10m/s2

v = gt

d = 0.5gt2                                                        


Newton's second law of motion

Net force, Fnet = ma [Units: N]


Weight, W = mg [Units: N]

Momentum, p = mv [Units: kg m/s]      

Impulse = Fnett = change in momentum = pf - pi

Kinetic energy, KE = 0.5mv2 [Units: J]

Gravitational potential energy, GPE = mgh [Units: J]     

Work, W = Fd [Units: J]

Gravitational force, F = GM1M2/r2 [Units: N]

For molecules at a particular temperature T, KE = 0.5mv2 = 3kBT/2

Heat energy, Q = mcDT [Units: J]

Heat energy, Q = mL [Units: J]

Wave speed, v = fl [Units: m/s]

Wave frequency, f = 1/T where T is the period in seconds [Units for frequency: Hz = 1/s]


Coulomb's Law (force between charged particles), F = kq1q2/r2    [Units: N]

Electrical  potential energy, EPE = V q       [Units: J]

Current, I = q/t             [Units: A]

Ohm's Law, V = IR          [Units: V]

Power, P = EPE/t = V I          [Units: W = J/s]


Quantities and units (in brackets)

distance, d (m)

time, t (s)

speed, v (m/s)

acceleration, a (m/s2), g (m/s2)

force, F (N); weight W(N)

mass, m (kg)

momentum, p (kg m/s)                                     

energy, KE, GPE, EPE (J)

work, W (J)

heat, Q (J)

specific heat capacity, c (J/kg C)

latent heat, L (J/kg)

temperature, T (C or K)

frequency, f (Hz or 1/s)

wavelength, l (m)


voltage, V (V, volts)

charge, q (C, coulombs)

current, I (A, amps)

resistance, R (W, ohms)

power, P (W, watts)



Speed of sound in air = 330m/s

Speed of light in a vacuum (or in air) = 3 x 108m/s = 300,000,000 m/s