Gravitational Potential Energy & Gravity
This lesson covers:
- What 'gravity' is
- What 'weight' is, and how to calculate it
- What 'gravitational potential energy' is, and how to calculate it
Mass & Weight
The terms 'mass' and 'weight' can be a bit confusing because we often use them to mean the same thing in every day life. In physics though, they're completely different - and it's important to understand that difference. |
An object's mass is an intrinsic property of that object. You can think of it as the "amount of stuff" in an object (or more technically the amount of 'matter'). Mass is measured in kilograms (kg) |
An object's weight refers to the force acting on that object due to gravity. This means that an object's weight can change depending on the strength of gravity (we refer to the strength of gravity as the 'gravitational field strength'). Weight is measured in newtons (N) |
What are the units of mass?
Newtons (N)
Joules (J)
Kilograms (kg)
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What are the units of mass?
Newtons (N)
Joules (J)
Kilograms (kg)
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True or false? The weight of an object is determined by both the strength of the gravitational field acting upon it, and the object's mass.
True
False
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What is the formula for weight?
Remember the symbols are:
Weight (W), mass (m), and gravitational field strength (g)
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What are the units of weight?
Newtons (N)
Joules (J)
Kilograms (kg)
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What is the weight of a 70 kg object on earth?
(The Earth's gravitational field strength is 9.8 N/kg)
70 N
7.1 N
686 N
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A car on earth experiences a downwards weight of 8820 N, what is the mass of the car?
(The Earth's gravitational field strength is 9.8 N/kg)
900 kg
86,436 N
900 N
86,436 kg
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Tony has a mass of 65 kg on Earth. What is Tony's mass on the moon?
kg
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Tony's mass is 65 kg. What is his weight on Earth? (The Earth's gravitational field strength is 9.8 N/kg) N
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What is Tony's weight on the moon? (The moon's gravitational field strength is 1.6 N/kg) N
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Every object in the universe exerts a force of gravitational attraction on every other object in the universe.
Which two factors determine the strength of the gravitational force of attraction?
The distance between the objects
The shape of the objects
The charge of the objects
The mass of the objects
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What are the units of gravitational potential energy (GPE)?
Kilograms (kg)
Newtons (N)
Joules (J)
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The value of the gravitational field strength on the Earth's surface is N/kg:
1.6
6.67
1.4
9.8
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What is the formula for gravitational potential energy?
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Tony, who has a mass of 65 kg, climbed the stairs from the ground floor, up to the fourth floor, which is 20 m higher. How much gravitational potential energy did Tony gain?
(The Earth's gravitational field strength is 9.8 N/kg)
J
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Freya, who has a mass of 60 kg, jumps from a boat into the sea. Just before she hits the water, she has lost 1,470 J of gravitational potential energy.
How far did she fall?
m
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Which of the following is a force?
Mass
Weight
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