GCSE · Physics · AQA · Spec 8463
Acceleration (a = Δv/t)
Every rocket launch, emergency stop, and skydive is defined by one number: acceleration.
What you need to know
- Acceleration is the rate of change of velocity: a = (v − u) / t
- Use v^2 − u^2 = 2 a s when time is unknown but distance is given — this equation is on your equation sheet
- Deceleration is simply a negative acceleration — the same equation applies, the value just comes out negative
- Near Earth's surface, free-fall acceleration is approximately 9.8 m/s²; terminal velocity occurs when drag equals weight so the resultant force is zero
The big picture
Acceleration measures how quickly velocity changes — not how fast something moves, but how fast its speed or direction is changing. A positive acceleration means speeding up; a negative acceleration means slowing down (deceleration). Near Earth's surface, freely falling objects accelerate at about 9.8 m/s², but drag eventually grows until it balances weight and terminal velocity is reached.
TONIGHT'S REVISION
Acceleration (a = Δv/t)
How quickly velocity changes — and why a falling object eventually stops accelerating
Forces on a falling object — at terminal velocity
Tap each force arrow to see what it does. Notice that the two arrows are equal in size — this is the key to terminal velocity.
Tap a force to see what it does.
Predict, then check
Commit to your answer before revealing — this is the exact thinking the examiner rewards.
A motorbike's velocity changes from 6 m/s to 30 m/s in 8 seconds. A student calculates acceleration as 30 ÷ 8 = 3.75 m/s². What is wrong, and what is the correct answer?
Terminal velocity — reason it through
Reason it through
Why does a skydiver eventually stop accelerating and fall at a constant speed?
First link · your turn
What happens to drag as the skydiver falls faster and faster?
Relationship matrix
Tap any cell to reveal it. Tap a column header to read one property down every item.
Each cell hides a short answer and the reason behind it. Predict before you tap.
AQA Paper 2 · Exam application
Mark scheme practice — AQA style
Read the student answer and see which mark-scheme phrases it hits.
Question
Explain why a skydiver reaches terminal velocity. (4 marks)
Student answer
As the skydiver falls, their speed increases. This means drag increases. The resultant force decreases because drag is getting closer to weight. When drag equals weight, the resultant force is zero, so acceleration is zero and the skydiver falls at a constant speed called terminal velocity.
Equations you need
Taken directly from the exam-board specification.
a = acceleration (m/s^2) · v = final velocity (m/s) · u = initial velocity (m/s) · t = time (s)
Learn it — you must recall this in the exam
v = final velocity (m/s) · u = initial velocity (m/s) · a = acceleration (m/s^2) · s = distance (m)
Given on the equation sheet — you must know how to use it
Key points
Worked example
Problem
A cyclist accelerates from rest to 12 m/s over 8 seconds. Calculate her acceleration.
Memory hook
Think of acceleration as the 'velocity speedometer's rate of change' — just as speed tells you how fast position changes, acceleration tells you how fast speed changes. Picture a sprinter: they don't instantly hit top speed, they build it second by second — that build-rate is acceleration.
★ Exam tip
On AQA Paper 2, if a question gives you two velocities and a distance but no time, reach straight for v^2 − u^2 = 2 a s from the equation sheet — identify it before you start working, not halfway through.
⚠ Watch out
Forgetting to subtract the initial velocity — if an object is already moving, you MUST use (v − u) in a = (v − u) / t, not just v. Using only the final velocity silently drops the 'change in' meaning.
Check yourself
Without looking: what is the acceleration of an object whose velocity changes from 25 m/s to 10 m/s in 5 seconds, and is this value positive or negative?
Flashcards
(25)What does acceleration measure?
Write the equation for uniform acceleration.
What are the units of acceleration?
What is deceleration in terms of acceleration?
What is the approximate acceleration due to gravity near Earth's surface?
What does terminal velocity mean?
Why is resultant force zero at terminal velocity?
An object accelerates from 5 m/s to 25 m/s in 4 s. What is a?
Which equation links velocity, acceleration and distance when time is unknown?
Is v^2 − u^2 = 2 a s recalled or given on the AQA equation sheet?
What does 'u' represent in the acceleration equations?
What does 'v' represent in the acceleration equations?
A car brakes from 30 m/s to 0 m/s in 6 s. What is the acceleration?
Why does a skydiver accelerate at first after jumping?
Why does a skydiver's acceleration decrease as they fall faster?
At terminal velocity, what is the value of acceleration?
A ball is dropped and falls freely (ignore air resistance). What is its acceleration?
What does a negative value of acceleration always mean physically?
What practical (RP7) is linked to acceleration at GCSE?
If u = 0 (starts from rest), how does v^2 − u^2 = 2 a s simplify?
What is the change in velocity (Δv) for an object going from 8 m/s to 20 m/s?
A stone is thrown upward. What is its acceleration during flight (ignore air resistance)?
Which AQA paper is acceleration assessed on?
An object travelling at 10 m/s accelerates at 3 m/s² for 5 s. What is its final velocity?
What happens to drag force as a falling object speeds up?
Tap any card to flip it, or use Study as deck to go through them one at a time. In the full lesson these run as a spaced-repetition deck — you rate each card Hard, Good or Easy and the tricky ones keep coming back until they stick.
Learn Acceleration (a = Δv/t) properly — interactive practice, marked questions and flashcards.
Start this lesson freeMore AQA GCSE Physics topics
- Current, resistance and potential difference (V = I R)
- Density of materials (ρ = m/V)
- Distance and displacement
- Distance–time graphs
- Efficiency
- Energy stores and systems
- Gravitational potential energy (Ep = m g h)
- Kinetic energy calculation (Ek = 1/2 m v^2)
- Newton's First Law
- Newton's Second Law (F = m a)
- Power (P = E/t and P = W/t)
- Resultant forces and resolving forces
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