Gravity and calculating weight

Large objects, such as the Earth, will produce a gravitational field. Masses inside the gravitational field will experience a force called weight.
Weight will pull the mass towards the centre of the field. On Earth, this will pull masses down toward its surface.
Weight will act through a single point in the object called its centre of mass. Smaller objects also produce gravitational fields, but the forces from these are too small to be noticed.
The weight of an object can be measured using a spring balance.
The weight an object experiences depends on its mass and gravitational field strength, given by \(\text{weight}=\text{mass}\times\text{gravitational field strength}\) or \(W = mg\)
- Mass is how much matter makes up an object. An object’s mass will be the same in any gravitational field at any point in the universe.
- Gravitational field strength is the force a 1 kg object would experience at a point in a gravitational field, given in N/kg. This will depend on location in the field and what is producing the field.
- On the Earth’s surface, the gravitational field strength has a constant value of 9.8 N/kg.This means that on Earth, mass is proportional to weight. However, on other planets, the weight of an object will change while its mass will not.

Sign up to unlock the rest of this topic — plus every other topic, video, flashcard set and eBook guide in your SnapRevise+ subscription.

Cancel anytime — instant access the moment you sign up.