Difference between velocity and speed.

1. Feb 16, 2010

Sirsh

A tennis ball of mass 10.0 g bounces vertically on a concrete floor. The ball strikes the floor at 20.0 m s–1 and rebounds at 15.00 m s–1.

5.
A. What is the change in speed of the ball as it bounces?

Δv = v1-v2
= 20ms-1 - 15ms-1
Δv = 5ms-1

B. What is the change in velocity of the ball as it bounces?

Δv = v1 - v2
= 20ms-1 – (-15ms-1)
Δv = 35ms-1

Does that depict the difference between speed and velocity as speed is a scalar quantity it doesnt have direction therefore when calculating (in this case) is a positive value, but when calculating the change in velocity because it is a vector quanitiy it has a direction ( negative because it's going in the opposite direction as the initial drop) so it has a negative value? Im not sure if this is correct. thank you.

2. Feb 17, 2010

ehild

You know it well, velocity is a vector quantity and speed is its magnitude, so a non-negative scalar. Well done!

ehild

3. Feb 17, 2010

Sirsh

Awesome, thank you (: