# Stuck on finding force

1. Sep 30, 2007

### bigtymer8700

1. The problem statement, all variables and given/known data

An adult 68.0kg cheetah can accelerate from rest to 20.1 (45.0mph ) in 2.00 s.

2. Relevant equations

F=MA
Vf=Vi + (a)t

3. The attempt at a solution

Assuming constant acceleration, find the net external force causing this acceleration

i solved for the time using Vf=Vi + (a)t. i got acc=10.05

when i tried plugging in the 10.05 for the acceleration and times the mass it gave me 684N. Its coming up wrong and I dont know where im messing up on

2. Sep 30, 2007

### Kurdt

Staff Emeritus
When I multiply 68 by 10.05 I get 683.4. I would guess its just a rounding error.

3. Sep 30, 2007

### Sourabh N

Are you sure its 684. you are messing up with the calculations, i suppose.

4. Sep 30, 2007

### bigtymer8700

yea actually did it would let you know if you where close but it says nothing about a rounding error

5. Sep 30, 2007

### bigtymer8700

actually no the computer was wrong thanks for the help though it was a glitch in the computer it has 2.01m/s as 45mph so it takes the right answer to be 68.3N. Man that is why I really hate online hw. but thanks anyway