motion
Speed, Velocity and Acceleration
Speed = the distance travelled per unit time i.e. distance ÷ time
Speed = Distance Moved
Time
Velocity – the speed in a particular direction.
Velocity = Distance Moved in a Particular Direction
Time
Acceleration – the rate of change of velocity i.e. by how much is the velocity changing per unit time.
Acceleration = Change in velocity
time taken
Positive acceleration means the velocity is increasing. Negative acceleration means the velocity is decreasing.
Acceleration = change in velocity ÷ time taken for velocity change =
final velocity – initial velocity
time taken for the change
Q Calculate the acceleration of a car if its velocity increased from 10 ms-1 to 30 ms-1 in five seconds.
Acceleration = change in velocity ÷ time taken
= final velocity – initial velocity
time taken for the change
= 30 ms-1- 10 ms-1
5 s
= 20 ms-1
5 s
= 4 ms-2
Q Calculate the acceleration of a car if it comes to rest from 40 m-1 in 8 seconds.
Acceleration = change in velocity ÷ time taken
= final velocity – initial velocity
time taken for the change
= 0 ms-1 – 40 ms-1
8 s
= - 40 ms-1
8 s
= -5 ms-2
The minus sign means the car is slowing down!!!