Calculating Weight (OCR GCSE Physics A (Gateway Science Suite)): Revision Notes
📚 Revision Notes
5.1.5 Calculating Weight
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The weight of an object and its mass are directly proportional. For a given gravitational field strength, the greater the mass of the object, the greater its weight.
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Weight can be calculated using the equation:
This is when:
- weight () is measured in newtons (N)
- mass () is measured in kilogrammes (kg)
- gravitational field strength () is measured in newtons per kilogramme (N/kg)
Rearranging:
| W = m x g |
|---|
| m = W ÷ g |
| g = W ÷ m |
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Example: What is the weight of a person with a mass of 55 kg?
Weight = mass x gravity
Weight = 55 x 10
Weight = 550 N
Measuring Weight
A Newton Meter
A mass suspended on the lower hook will pull the spring inside and move the indicator along the scale.
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The scale is calibrated to newtons. We can use a Newton metre to measure the weight of an object, in Newtons.
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Key Points:
- Weight is a force and is measured in newtons.
- It is different from mass, which is a measure of the amount of matter in an object and is measured in kilogrammes.
- Weight changes with the strength of the gravitational field, but mass remains constant.