13 5.2 A motion diagram: the car that gains 5 m/s every second
A car starting from rest has the following speedometer readings:
1velocity (m/s)
0
- 0
1
- 5
2
- 10
3
- 15
4
- 20
The velocity increases by 5 m/s every second — a constant rate. This rate is the acceleration:
a = Δv / Δt = (v₂ − v₁) / (t₂ − t₁)
Check with the table: between t = 1 s and t = 2 s, a = (10 − 5)/(2 − 1) = 5 m/s².
Acceleration
- is the change in the velocity of the body per unit time, i.e.
- the time rate of change of velocity.
- Unit: m/s² (SI) or km/h².
- It is a vector quantity.
- Its dimensional formula is LT⁻².
Meaning of "5 m/s²": every second the velocity changes by 5 m/s.