# Kinematics Problem. Help

1. Jan 9, 2014

Ok so I have this problem which is most likely easy to all of you. The problem says that the first 10 meters of the 100 meter are covered in the first 2 seconds by a sprinter who starts from rest and accelerates with a constant acceleration. The remaining 90 meters are run with the same velocity the sprinter had after 2 seconds.
a. Determine the sprinters constant acceleration during the first 2 seconds. I got 5 m/s

b. Determine the sprinters velocity after 2 seconds have elapsed. I couldn't decide on 5 m/s^2 or 10 m/s^2 because i used Vf=Vo+at and V=d/t and it gave me those two different answers.

c. Determine the total time needed to run the full 100 meters. I got 6.32s which is unrealistic.

Please help me out I'm a little rusty just starting physics two and would love for you guys to solve and compare answers. Thank you!

2. Jan 9, 2014

### voko

What are the units of acceleration?

One of these formulas applies to uniformly accelerated motion. Another to motion with constant velocity. What is the case here? And, again, watch out for correct units.

Explain how you got that.

3. Jan 9, 2014

### Malverin

You have the time (t= 2 s), and the distance (y= 10 m), so you can easy calculate the acceleration.