Homework Help: Trouble finding the acceleration

1. Sep 23, 2007

danni7070

A block of mass m1 is attached to a massless, ideal string. This string wraps around a massless pulley and then wraps around a second pulley that is attached to a block of mass m2 that is free to slide on a frictionless table. The string is firmly anchored to a wall and the whole system is frictionless.

I want to find the vertical acceleration a1 in terms of m1, g and T

I know that the tension T is equal everywhere in the string and also that the acceleration af block m1 must be equal to the acceleration of block m2.

I've tried some calculations but I always seem to get stuck with m2 in my equations.

T = m1*g and T = (m2*a2)/2

Last edited: Sep 23, 2007
2. Sep 23, 2007

mgb_phys

The setup is that a falling weight M1 pulls a mass M2 horizontally - correct.
The force downward on M1 is just f = M1 g and the force upward from the string is f = M2 a

3. Sep 23, 2007

danni7070

Yeah, I figured that one out but that was not the question (but thanks thanks anyway for replying! :)

My problem is to find the a1 in terms off m1, g and T (When T = (m2*a2)/2)

4. Sep 23, 2007

danni7070

Ok. I've got the answer! Was a bit hard but finally.

a1 = (m1-g)/m1

5. Sep 23, 2007

tabchouri

are you sure ?
i did not do the math, but the UNIT of (m1-g)/m1 is not a unit of acceleration

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