AQA GCSE Physics
AQA GCSE Physics 4.5.1.3 Gravity Exam Questions
Free AQA GCSE Physics exam questions for 4.5.1.3 Gravity, with a mark scheme for every pack. Covers weight, mass, gravitational field strength, W = mg, centre of mass and measuring weight with a newtonmeter.
4.5.1.3 Gravity exam questions
2 question packs of real past exam questions, each with its mark scheme. Do not stop after a few: answer as many as you can without notes, then mark every answer with the mark scheme. The more questions you do, the more quickly you will spot how examiners ask about each idea.
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About AQA GCSE Physics 4.5.1.3 Gravity
This AQA GCSE Physics section covers weight, the force acting on an object due to gravity. You need to use W = m g, explain the difference between mass and weight, and understand the centre of mass. It is examined on Paper 2, and the same gravitational field strength idea appears in gravitational potential energy (4.1.1.2), pressure in fluids and space physics. Examiners test calculations, especially on other planets, and the precise difference between mass and weight.
What you need to know
- Weight Weight is the force acting on an object due to gravity. The force of gravity close to the Earth is due to the gravitational field around the Earth.
- W = m g W = m g, where W is weight in newtons (N), m is mass in kg and g is gravitational field strength in N/kg. On Earth g is about 9.8 N/kg. This must be memorised.
- Mass and weight Mass is the amount of matter in an object and is the same everywhere. Weight depends on the gravitational field strength at the point where the object is. Weight and mass are directly proportional.
- Centre of mass The weight of an object may be considered to act at a single point referred to as the object's centre of mass.
- Measuring weight Weight is measured using a calibrated spring-balance (a newtonmeter).
- Other planets Gravitational field strength is different on other planets and moons (lower on the Moon), so an object's weight changes but its mass stays the same.
Common mistakes in 4.5.1.3 Gravity
- Giving weight in kilograms. Weight is a force and is measured in newtons.
- Saying mass changes on the Moon. Mass stays the same; weight decreases because g is smaller.
- Forgetting to convert grams to kilograms before using W = m g, giving a weight 1000 times too big.
- Saying weight acts from the bottom of an object. It acts from the centre of mass.
Try three 4.5.1.3 Gravity exam-style questions
1. Calculate the weight of a 65 kg person on Earth. g = 9.8 N/kg. (2 marks)
Show the mark scheme answer
W = m g = 65 x 9.8; = 637 N (accept 640 N).
2. An astronaut has a mass of 80 kg. On the Moon her weight is 128 N. Calculate the gravitational field strength on the Moon. (2 marks)
Show the mark scheme answer
g = W / m = 128 / 80; = 1.6 N/kg.
3. Explain the difference between mass and weight. (2 marks)
Show the mark scheme answer
Mass is the amount of matter in an object (in kg) and does not change with location; weight is the force due to gravity on that mass (in N) and depends on gravitational field strength.
4.5.1.3 Gravity FAQs
What does AQA GCSE Physics 4.5.1.3 Gravity cover?
It covers weight as the force due to gravity, the equation W = m g, the difference between mass and weight, centre of mass and measuring weight with a newtonmeter.
What value of g should I use?
Use the value given in the question. On Earth it is about 9.8 N/kg, and some questions round this to 10 N/kg.
What equation must I memorise for gravity?
W = m g. Practise rearranging it to find mass or gravitational field strength.
