a) Mass and weight

a) net force = mass × acceleration; F = ma

b) the newton as the unit of force

c) weight of an object; W = mg

F = ma

• resultant force (N) = mass (kg) × acceleration (ms^-2)

W = mg

• weight (N) = mass (kg) × acceleration of free fall (ms^-2)

to measure an object’s weight

• hang the object on a newtonmeter

• the reading on the newtonmeter gives the weight