# Homework Help: Forces and kinetic energy problem

1. Oct 25, 2009

### kza62

1. The problem statement, all variables and given/known data
Shawn and his bike have a total mass of 43.5 kg. Shawn rides his bike 1.3 km in 10.4 min at a constant velocity.
The acceleration of gravity is 9.8 m/s^2
What is Shawn's kinetic energy?

2. Relevant equations
F = ma
Ff = u * Fn
Fn = mg
avgV = x/t
x = 1/2(Vf + Vi)t

3. The attempt at a solution

ok so I converted km to m and min to s:
x = 1300m
t = 624s
and then i used avgV = x/t so avgV = ~2.08333 m/s

i have no idea what kinetic energy is, this hasn't been covered in class yet but I wanted to get ahead because I think I am coming down with the flu. The answer to the problem is supposed to be 94.4014 J but I have no idea how to set this problem up to get this. Please help me! Thanks.

2. Oct 26, 2009

### rl.bhat

The kinetic energy = 1/2*m*v^2

3. Oct 26, 2009

### kza62

THAAATTSS what i needed ooohhh maaann thanx rl.bhat!
so it would be (0.5)(43.5)(2.08333)^2 = 45.3124 J

thanks again!