# Homework Help: A crane problem kinematics

1. Mar 13, 2017

1. The problem statement, all variables and given/known
G=8400N
h=35m
d=10m
g=10m/s^2

A crane elevate a box with G=8400N at h=35. After this, the box is moved horizontal on distance 10m. No friction.

Work = ?
2. Relevant equations
I think that W=W1 ( work on elevating ) + W2 ( work on moving ).
W1=F1*h and W2=F2*d

In the first I must tu find F1.
F=F1-G ==> F1=G-F=G-ma

Now, F2:
F=F2==> F2=m*a.

W=F1+F2=G-ma+m*a.

But I don't know a...
3. The attempt at a solution

I know I am bad but I want to learn. What can I do to solve this exercice ? Thank you very much !

2. Mar 13, 2017

### BvU

Assume the lifting goes very slowly. So the only force that is needed for that is $mg$ = G . Keep the direction of the force in mind.
(why do I say that?).

3. Mar 13, 2017

Because F = -G ? Or.. F is a little bit stronger that G to lift ?

Last edited: Mar 13, 2017
4. Mar 13, 2017