Speed

John walks along a green path of 2500m from the Start to the End in 50 minutes.

What is Speed?
It is the distance travelled per unit time.

• A scalar quantity (i.e. has magnitude only)
• SI unit: metre per second (m s⁻¹)
• The distance travelled by john is the total length of the path which is 2500m.

What is the speed of John?

Speed=2500/3000
=0.83m s⁻¹ (2dp)

John is travelling at at speed of 0.83m s⁻¹

What is Average Speed?

Classic Speed Questions

1. An athlete initially at rest, runs a 100 m race and completed it with an average speed of 13.2 m/s. Explain why at some point in time his instantaneous speed must have exceeded the average value.

• Since the athlete starts from rest, he must have had a speed of less than 13.2 m/s during his acceleration.
• Therefore, his speed at other parts of the race must exceed 13.2 m/sin order for the average to be obtained as 13.2 m/s