HELP ON A WORK PROBLEM CAN'T DO IT BY MYSELF SNIFF SNIFF.:cry:

[Min_Shin]

a uniform ladder of mass 12kg is 4.6m long. if it is lifted from a horizontal to a vertical position, how much work is done

i just thought because i have to lift the centre of the mass, i'd have to do mgh with h being 2.3m. I think i am sure that i don't have the right answer. Sniff.. help please!

 

[Harmony]

I think you are correct.

 

[Min_Shin]

HAHA... oh... thanks.

 

[arildno]

The work must equal the potential energy increase for the ladder (since there isn't any kinetic energy relevant for this problem).

But the potential energy increase for the WHOLE ladder, is simply the ladder's mass multiplied with g and the C.M's position, since the gravitational potential energy is linear in the vertical position coordinate.