Average velocity and average speed problem.

[afcwestwarrior]

Homework Statement

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.

Homework 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

 

[LowlyPion]

Homework Statement

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.

Homework Equations

this asks for average velocity which equals=change of x/change of t or xfinal-xinitial/tfinal-tinitialisn't acceleration = change of velocity over/ change of time

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

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

 

[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

 

[LowlyPion]

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

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?

 

[afcwestwarrior]

It takes 60 seconds.

 

[LowlyPion]

It takes 60 seconds.

OK. Now how long for the second leg?

 

[afcwestwarrior]

It takes 24 seconds

 

[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?

 

[afcwestwarrior]

ok so it would be 73.2+73.2=146.4

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

 

[afcwestwarrior]

wait a minute would i add the time together

 

[LowlyPion]

wait a minute would i add the time together

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?

...this asks for average velocity which equals=change of x/change of t ...

 

[afcwestwarrior]

oh yeah huh.

 

[afcwestwarrior]

yes i did