Find average speed and average velocity.?

Question

Starting from a pillar,you run 200m east(the +x-direction) at an average speed of 5.0m/s,and then run 280m west at an average speed of 4.0m/s to a post. Calculate your average speed from pillar to post & your average velocity from pillar to post

Answer 1

You first run 200 m east at 5m/s so it takes you 200/5 = 40 seconds

Then you run 280 m west at 4 m/s so it takes you 280/4 = 70 seconds

So your trip took 110 seconds.

In total you ran 480 meters in 110 seconds

So your speed is 480/110 = 4.3636 m/s

For velocity, you must look at displacement.

You went 200 - 280 m = -80 meters  (on the x axis), so 80 meters west

so your velocity is 80/110 meters/s west

which is 0.7272 m/s west.