Linear Motion

Definition - movement of a body in a straight or curved line, where all parts move the same direction over the same time

Direct Force - a force applied through the centre of mass resulting in linear motion

Linear motion results from a force applied directly to the centre of a body's mass

e.g. water skier on flat lake being pulled at constant speed will travel in linear motion as all parts of body travel in same direction over same distance per unit of time

Distance:

• total length of path covered from start to finish
• measured (m)
• e.g. swimming 4 lengths of 50m pool = 200m

Displacement:

• shortest straight line route from start to finish
• measured (m)
• e.g. swimming 4 lengths of 50m pool = 200m

Speed:

• rate of change in distance
• speed = distance/time taken
• m/s
• e.g. 200m world record is 21.63s - 200m/21.63 = 9.25m/s average speed

Velocity:

• rate of change in displacement
• velocity = displacement/time taken
• m/s
• e.g. 100m world record 9.58s - 100m/9.58 = 10.44m/s average velocity

Acceleration + Deceleration:

• the rate of change in velocity
• acceleration + deceleration = (final velocity - initial velocity)/time taken
• m/s/s
• e.g. 9.58 100 metres - first 20m time = 2.89s - velocity at 20m = 6.92 m/s - veloctiy at 0m = 0
• change in velocity = 6,92m/s - average acceleration over first 20m = 2.39 m/s/s (6.92/2.89)

Velocity/time graphs are same but can be negative to show direction change