Course: Combined Science + Separate Physics | Tier: Foundation | Next: Speed–time graph activity
✏️ You need: your exercise book and a calculator. Write out every step before you open the answer.
📌 KEY DEFINITIONS – learn them word for word
Acceleration is how quickly the speed changes.
Acceleration = change in speed ÷ time taken
Unit of acceleration: m/s² (metres per second squared). Deceleration means slowing down.
🎬 Watch first: Free Science Lessons video
Watch this short video, then read the notes below. Pause it and copy the equation into your book.
📖 Notes
What is acceleration?
An object accelerates when its speed changes.
- Speeding up = accelerating 🚀
- Slowing down = decelerating 🛑
- Same speed = no acceleration (acceleration = 0)
What does 2 m/s² mean?
An acceleration of 2 m/s² means the speed goes up by 2 m/s every second.
| Time (s) | 0 | 1 | 2 | 3 | 4 |
| Speed (m/s) | 0 | 2 | 4 | 6 | 8 |
A bigger acceleration means the speed changes more quickly.
Real-life accelerations
| Object | Typical acceleration |
|---|---|
| 🚶 Person starting to walk | about 1 m/s² |
| 🚗 Family car pulling away | about 3 m/s² |
| 🪨 Object falling (no air resistance) | about 10 m/s² (9.8 m/s²) |
| 🏎️ Racing car | about 10 m/s² or more |
🧮 How to calculate acceleration – 3 steps
Step 1 – Change in speed = final speed − starting speed
(If it starts “from rest”, the starting speed is 0.)
Step 2 – Time taken in seconds (s).
Step 3 – Divide: acceleration = change in speed ÷ time
Write the unit: m/s²
✅ Worked example
A car speeds up from 10 m/s to 25 m/s in 5 seconds. Calculate its acceleration.
Step 1: Change in speed = 25 − 10 = 15 m/s
Step 2: Time = 5 s
Step 3: Acceleration = 15 ÷ 5 = 3 m/s²
🔍 See the acceleration formula triangle
✏️ Questions
Level 1: What does it mean?
Q1 A bus is travelling at a steady 12 m/s. What is its acceleration?
Show answer
0 m/s² – its speed is not changing.
Q2 A skateboarder has an acceleration of 3 m/s². By how much does her speed go up each second?
Show answer
Her speed goes up by 3 m/s every second.
Level 2: Starting from rest
Q3 🚲 A bike starts from rest and reaches 10 m/s in 5 seconds. Calculate its acceleration.
Show answer
Change in speed = 10 − 0 = 10 m/s
Time = 5 s
Acceleration = 10 ÷ 5 = 2 m/s²
Q4 🚗 A car starts from rest and reaches 20 m/s in 4 seconds. Calculate its acceleration.
Show answer
Change in speed = 20 − 0 = 20 m/s
Time = 4 s
Acceleration = 20 ÷ 4 = 5 m/s²
Q5 🏃 A sprinter starts from rest and reaches 8 m/s in 2 seconds. Calculate her acceleration.
Show answer
Change in speed = 8 − 0 = 8 m/s
Time = 2 s
Acceleration = 8 ÷ 2 = 4 m/s²
Level 3: Already moving – find the change in speed first
Q6 🚌 A bus speeds up from 5 m/s to 15 m/s in 5 seconds. Calculate its acceleration.
Show answer
Change in speed = 15 − 5 = 10 m/s
Time = 5 s
Acceleration = 10 ÷ 5 = 2 m/s²
Q7 🚙 A car on a motorway speeds up from 20 m/s to 30 m/s in 5 seconds. Calculate its acceleration.
Show answer
Change in speed = 30 − 20 = 10 m/s
Time = 5 s
Acceleration = 10 ÷ 5 = 2 m/s²
Q8 🏎️ Which is faster to speed up? A sports car goes from 0 to 30 m/s in 5 seconds. A family car goes from 0 to 30 m/s in 10 seconds. Calculate both accelerations. Which car has the bigger acceleration?
Show answer
Sports car: 30 ÷ 5 = 6 m/s²
Family car: 30 ÷ 10 = 3 m/s²
The sports car has the bigger acceleration – it reaches the same speed in less time.
Level 4: Slowing down (deceleration)
Tip: work it out the same way. Take the smaller speed away from the bigger speed. The answer is the deceleration.
Q9 🛑 A car travelling at 20 m/s brakes and stops in 4 seconds. Calculate its deceleration.
Show answer
Change in speed = 20 − 0 = 20 m/s
Time = 4 s
Deceleration = 20 ÷ 4 = 5 m/s²
Q10 🚆 A train slows down from 30 m/s to 10 m/s in 10 seconds as it comes into a station. Calculate its deceleration.
Show answer
Change in speed = 30 − 10 = 20 m/s
Time = 10 s
Deceleration = 20 ÷ 10 = 2 m/s²
Level 5: Challenge – work backwards
Use the formula triangle: change in speed on top, acceleration × time underneath.
Change in speed = acceleration × time · Time = change in speed ÷ acceleration
Q11 🚗 A car starts from rest and accelerates at 3 m/s² for 4 seconds. What speed does it reach?
Show answer
Change in speed = 3 × 4 = 12 m/s
It started at 0, so it reaches 12 m/s
Q12 🛵 A scooter starts from rest and accelerates at 2 m/s². How long does it take to reach 12 m/s?
Show answer
Change in speed = 12 − 0 = 12 m/s
Time = 12 ÷ 2 = 6 s
⚠️ Where students lose marks
- Dividing the final speed by the time when the object did not start from rest. Always find the change in speed first.
- Getting the division the wrong way round. It is always speed ÷ time, not time ÷ speed.
- Writing the wrong unit. Speed is m/s, but acceleration is m/s².
- Thinking constant speed means acceleration. If the speed does not change, the acceleration is 0.
Next: Speed–time graph activity · F = ma: find the resultant force first · More acceleration questions
