# Average velocity and average speed problem.

1. Aug 28, 2008

### afcwestwarrior

1. The problem statement, all variables and given/known data
Compute your average velocity in the following 2 cases: (a): You walk 73.2 m at a speed of 1.22 m/s and then run 73.2 m at a speed of 3.005 m/s along a straight line.

2. Relevant equations
this asks for average velocity which equals=change of x/change of t or xfinal-xinitial/tfinal-tinitial

isn't acceleration = change of velocity over/ change of time

so what do i do, because it gives me two velocities

2. Aug 28, 2008

### LowlyPion

How long did it take you to accomplish the circuit? Vavg is defined as what? You know change of x, so ...?

3. Aug 28, 2008

### afcwestwarrior

Ok. I'm assuming that you add both of the velocities. 1.22 m/s+ 3.05 m/s=4.27m/s
My total distance was 73.2 m + 73.2 m=146.6 m

4.27m/s / 146.6 m=.0291268759 seconds

4. Aug 28, 2008

### LowlyPion

I think you've used an invalid approach.

The sum of the velocities divided by the total distance is not equal to the time.

How long does it take to do the first leg - 73.2 m at 1.22 m/s?

5. Aug 28, 2008

### afcwestwarrior

It takes 60 seconds.

6. Aug 28, 2008

### LowlyPion

OK. Now how long for the second leg?

7. Aug 28, 2008

### afcwestwarrior

It takes 24 seconds

8. Aug 28, 2008

### LowlyPion

Knowing total distance and total time now you are in position to calculate avg velocity. This is given by which of the equations you cited in your first post?

9. Aug 28, 2008

### afcwestwarrior

ok so it would be 73.2+73.2=146.4

146.4m/60s-24s=4.07m/s

10. Aug 28, 2008

### afcwestwarrior

wait a minute would i add the time together

11. Aug 28, 2008

### LowlyPion

Well I sure would. Not sure why you would subtract time in this case. You want total time.

You did post this didn't you?

12. Aug 28, 2008

### afcwestwarrior

oh yeah huh.

13. Aug 28, 2008

yes i did