A man decided to run a marathon.
(a) What was his average speed, in m/s, for the first 5K?
(b) At 5K, was he speeding up or slowing down? Explain.
a) change in distance/time
b) acceleration = change in velocity/ change in time
The Attempt at a Solution
So for part a I simply solve for average speed which is change in distance / time. I get 3.87m/s (I believe this is the right sig digs)
part b I'm not too sure if I am doing it right. I believe for him to be speeding up there needs to be acceleration @ 5K. So now I solve if there is acceleration at 5k. I start by doing acceleration = change in velocity / change in time.
So a = (3.87m/s - 0m/s) / (1292s - 0s)
a= 0.0039953 m/s^2
So the acceleration at 5k is 3.0x10^-3 m/s^2. And since there is some form of positive acceleration found at 5K, this means he is in fact speeding up at 5K.
Am I correct for part B, or completely wrong? I need help.