# Homework Help: Work and energy difficulty

1. Apr 17, 2008

### ka7

[SOLVED] Work and energy

Hello, I've been having difficulty with this question...
1. The problem statement, all variables and given/known data

A 25.6kg child pulls a 4.81kg toboggan up a hill inclined at 25.7° to the horizontal. The vertical height of the hill is 27.3 m. Friction is negligible. Determine how much work the child must do on the toboggan to pull it at a constant velocity up the hill.

2. Relevant equations

W=FD COS (ANGLE)

3. The attempt at a solution

I tried using the equation above...and i tried adding the masses ...I got the wrong answer. The force, I used F=mg
w=mgd cos (angle)
=(4.81) (9.8) (27.3) cos (25.7)
=1.15 x 10^3 J
the answer 1.29 x 10^3 J but i'm not geting that...

2. Apr 17, 2008

### Hootenanny

Staff Emeritus
Welcome to the forums ka7,

HINT: What is the change in gravitational potential energy of the toboggan? (Much easier )

3. Apr 17, 2008

### Pere Callahan

You should recheck what the D in your formula means. It is presumably NOT the vertical height of the hill.

4. Apr 17, 2008

### ka7

Thanks, i figured out what i was doing wrong