Newton's law problem have attempted it

1. Oct 6, 2005

thugg

Newton's law problem....have attempted it

http://img128.imageshack.us/img128/2941/asd6rh.jpg [Broken]

rope is of negligible mass and no friction.....now this is what i did

the bc and ab are subscripts for cords between each block

9.8(10)- Tbc = 10a
9.8(40)-Tab = 40a
Tab=30a

so by substituting i get a =5.6

then i plug it in to get Tbc.....which gives me 42N.

but the answer in the book says 36.8N.....dunno what im doing wrong, any ideas?

Last edited by a moderator: May 2, 2017
2. Oct 6, 2005

Tom Mattson

Staff Emeritus
This is OK.

This is not OK.

You've got the weight of the 40 kg block and the tension pulling upwards, which is good. But Tbc is also acting on the 40 kg block, and you've left that out.

That's the only mistake I see, so that should fix the problem.

3. Oct 6, 2005

Tom Mattson

Staff Emeritus