# Homework Help: Circular motion: Speed, velocity for car on a semi-circular path

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1. Nov 25, 2016

### MPZ

1. The problem statement, all variables and given/known data
A car moves from X to Y along a semicircular path. The radius of the path is 250 m and the time taken to complete the trip is 50 s.
What is the magnitude of the average velocity and the magnitude of the average speed?

2. Relevant equations
v = wr = 2π r/ T , a = v^2/r
T: period
3. The attempt at a solution
I figured out that the average velocity is 10 m/s , but why is the average speed 16 m/s

Last edited: Nov 25, 2016
2. Nov 25, 2016

### Orodruin

Staff Emeritus
What is the difference between velocity and speed?

Also, speed and velocity are measured in m/s. The unit m/s^2 is used for acceleration.

3. Nov 25, 2016

### MPZ

velocity is a vector (with direction) while speed is a scalar , also i will fix the unit now

4. Nov 25, 2016

### Orodruin

Staff Emeritus
So how would you compute the average speed and the average velocity, respectively?

5. Nov 25, 2016

### MPZ

average velocity using v = wr , average speed = (v at y + v at x)/2 ???

6. Nov 25, 2016

### Staff: Mentor

No, neither of the above are correct for this problem. You need to take a minute to look up the definitions of average speed and average velocity. The Hyperphysics website page for average velocity is apropos. Pay particular attention to the section, "Average Velocity, General".

Please don't "bump" your thread by posting appeals for a response when only a few minutes have passed since the last reply. Forum rules regarding thread bumping allow one bump after 24 hours have elapsed.

7. Nov 25, 2016

### rcgldr

Average velocity is the distance between starting and ending points divided by elapsed time, so it is independent of the path. Average speed is the distance traveled divided by elapsed time, so it is dependent on the path.