# 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!!!