Solved: Simple Force Problem: 80KG Man Exerts 20N

[Slayergnome]

Homework Statement

An 80 KG man is standing on the platform of mass 20 KG is lowering him self down using a massless cable passing over two pullies. If his downward acceleration is .2 M/S^2, find force exerted by the man on the cable.

Homework Equations

I thought it was a simple
F=M*A

The Attempt at a Solution

F= (100 Kg) * (.2 m/s^2)
F= 20 N

 

[Thrawn]

That is correct, provided gravity is ignored.

If you do not intend to ignore gravity, remember that gravity exerts a force of 9.8 N (g) at the surface of the Earth.

 

[Slayergnome]

I am and idot, thanks for the gravity tip also ther is a diagram I did not provide taht is very important, just out of curiosity do you put pictures on here using HTML type.

Calculation is
-980 + 3t=100kg*.2
3t=-20+980
t=320 N
The reason it is 3t is because the diagram shows the rope connecting the celling and the platform/man 3 times with the two pullys)

 

[Thrawn]

I am and idot, thanks for the gravity tip also ther is a diagram I did not provide taht is very important, just out of curiosity do you put pictures on here using HTML type.

Calculation is
-980 + 3t=100kg*.2
3t=-20+980
t=320 N
The reason it is 3t is because the diagram shows the rope connecting the celling and the platform/man 3 times with the two pullys)

I believe HTML is disabled, although you could upload the image and use IMG tags, I believe.