Velocity and Speed

Velocity vs Speed

• Velocity is a vector, speed a scalar• Average speed – total distance divided by

time• Average velocity – total displacement

divided by time• Speed and velocity may or may not have

the same magnitude

Example

• A person walks 70 m (E), then 30 m (W) in 70 sec. Find his a) speedb) velocity

Average Velocity Equation

• v = Δx/ Δt

• If v is +, moving to the right• If v is - , moving to the left

• This does not mean that the object traveled at this velocity the entire time!

Examples

• During a 3.00 s time interval a runners position changes from 50.0m to 30.5m. What is the average velocity over this time?

• How far can a cyclist travel in 2.5 hr along a straight road if her average velocity is 18km/hr?

Practice1) A girl throws a ball 10m straight up from

the top of a building that is 30m tall. A) What is the total distance the ball travels. B) What is the balls displacement

2) If it took the ball in the last problem 5.8 sec to hit the ground what is the A) speed B) velocity

3) A person drives at an average velocity of 25 km/h for 15 minutes. How far did they go?

4) A man runs half the distance of a circular track (of radius 15 m) in 1.0 minutes. What is his

a) distance traveledb) displacementc) speedd) velocity