Formulae - Physics

 FORMULAE

Making measurements

• density = mass/volume (g/cm3)

Describing Motion

• average speed = total distance travelled/total time taken (m/s)

• speed = distance/time (m/s)

• acceleration = change in velocity/time taken (m/s)

acceleration = new speed - old speed/time taken

Forces and Motion

• gravitational field strength = weight/mass (N/kg)

• weight = mass * gravity (N)

• force = mass * acceleration (N/m)

• momentum = mass * velocity (kg m/s)

• impulse = force * time (Ns)

• resultant force = change in momentum/unit time (N)

Turning effects of forces

• moment of a force = force * perpendicular distance from the pivot (Nm)

Forces and matter

• Force = constant(k) * extention(x)

• spring constant = force/unit extension

• pressure = force/area (N/m2 or pascals)

• change in pressure = density * gravity * depth (pascals)

Energy stores and transfers

• Efficiency = useful energy output/total energy input(*100 for percentage)

• change in g.p.e = weight * change in height

• Kinetic energy = 1/2 * mass * speed^2

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Work and Power

• Power = work done/time taken (Watts or Joules/second - Energy transfers)

• Work = force * distance (Nm or Joules Energy transfers)
  Work = mass * gravity * height

• Efficiency = useful power output/power input * 100

Thermal properties of matter

• specific heat capacity = Energy required/mass * temperature increase