## 2013-12-08

### Linear Motion Calculation Examples

A bicycle moved from point A and then moved 50 m to the north in 60 seconds. The bicycle then moved 120 m to the east in 40 seconds. Finally, it stopped. Calculate the

1. Total distance moved by the bicycle
2. Displacement
3. Velocity
4. Average speed
5. Speed of the bicycle when it is moving to the north

Solution:

1. Total distance = 50m + 170m
= 170m

2. Displacement

Remember displacement is the shortest distance between two points.

Imagine A as the beginning of a triangle.  Then connect it with a line of 50m upwards then it turns left 120m (go east). so the distance is the hypotenuse.

Using Pythagoras' theorem = Squared root (120^2 + 50^2)
= 130m

3. Velocity = Displacement / time

= 130 m / 100 s
= 1.3 m s^-1

4. Average speed of the bicycle = total distance / total time

= 170m/ 100s
= 1.7 m s^-1

5. Speed = distance / time

Distance = 50m, time = 60s

= 50m / 60s

= 0.83 ms^-1

Be careful during calculation as most of the time Physics requires a good skill in maths!!