Acceleration
Physics: Cambridge International GCSE Supplement, topic 1.2.4
Acceleration
Acceleration is defined as the change in velocity per unit time. This means how quickly the velocity of an object changes.
Acceleration and deceleration
- If an object is moving and its speed increases, it is said to be accelerating. For example, a car speeding up from traffic lights is accelerating.
- If an object is moving and its speed decreases, it is said to be decelerating. For example, a car slowing down as it approaches a stop sign is decelerating.
Negative acceleration
- Deceleration is simply negative acceleration.
- It happens when an object slows down, so the change in velocity is in the opposite direction to the motion.
- In calculations, this is shown by a negative value for 𝑎
- For example:
- A car slows from 20 m/s to 10 m/s in 5 seconds.
- 𝑎 = (10 - 20) / 5 = -10 / 5 = -2 m/s2
- The negative sign shows the car is decelerating.
Test yourself on Acceleration
A ball rolling down a hill accelerates uniformly from rest to a velocity of 5 m/s in 10 seconds. What is the acceleration of the ball?
A car slows from 20 m/s to 10 m/s in 5 seconds. What is the acceleration of the car?