Gravity — AQA GCSE Physics
Test yourself on Gravity with AQA GCSE practice questions.
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Gravity explained
Weight is a force, so it is measured with a calibrated spring-balance, also called a newtonmeter, which reads directly in newtons.
Read the full explanation
Inside, a spring extends when the object is hung from it. Because the extension is directly proportional to the force applied, the scale is linear with evenly spaced divisions, which makes the instrument straightforward to calibrate. The spring must deform elastically so that it returns to its original length once the object is removed; if it is overloaded so far that it deforms inelastically it stays stretched and the readings are wrong afterwards; past the limit of proportionality the scale also stops being evenly spaced. To use it well, zero it first, hang it vertically, let the object come to rest and read the scale at eye level.
Your focus
- Name the instrument used to measure weight and state the unit it reads.
- Explain two properties of a spring that make it suitable for a newtonmeter.
- Describe how to take an accurate reading from a spring-balance.
Gravity exam tips
Marking Points
- one mark for naming the instrument as a calibrated spring-balance or newtonmeter, reading in newtons
- one mark for the extension of the spring being directly proportional to the force, giving an evenly spaced scale
- one mark for the spring deforming elastically, so it returns to its original length when the force is removed
- one mark for a correct technique, such as zeroing the instrument and reading the scale at eye level with the object stationary
Examiner Tips
- 💡If asked why a spring suits this job, give the elastic deformation and the linear scale as two separate points.
- 💡Say the instrument is 'calibrated' in newtons; that word is in the specification and signals you know it reads force.
- 💡Mention eye level and a stationary object when a question asks how to improve accuracy.
Common Mistakes
- naming a top-pan balance, which measures mass in grams rather than weight in newtons
- reading the scale while the object is still swinging
- failing to zero the newtonmeter before hanging the object on it
- recording the reading in kilograms
- overloading the spring past its limit of proportionality and continuing to use the readings