What is the solution to the Moving Blocks Problem?

[zzinfinity]

Homework Statement

I'm stuck on this one,

A 32.5-kg block (m1) is on a horizontal surface, connected to a 6.9-kg block (m2) by a massless string as shown in the Figure. The pulley is massless and frictionless. A force of 223.3 N acts on m1 at an angle of 30.1o. The coefficient of kinetic friction between m1 and the surface is 0.213. Determine the upward acceleration of m2.

Homework Equations

The Attempt at a Solution

I determined the net force on m1 as follows

F=223.3Cos(30.1)-(m1*g-223.3Sin(30.1))*.213 - m2*g.

Then I determined the acceleration of m1 by dividing the net force by 32.5kg. I assumed that the acceleration of m1 and m2 should be the same so i got an answer of 2.51 m/s^2.

The online homework says this is wrong, what am I missing?

Thanks!

 

[grzz]

figure?

 

[zzinfinity]

Here it is

 

[grzz]

I determined the net force on m1 as follows

F=223.3Cos(30.1)-(m1*g-223.3Sin(30.1))*.213 - m2*g.

Why is the term m2*g in the above equation?

 

[zzinfinity]

The weight of m2 creates tension on the rope, which exerts a rightward force on m1, so don't you have to factor that into the net force on m1? m2*g is the weight of m2.

 

[grzz]

The weight of m2 creates tension on the rope, which exerts a rightward force on m1

The above is correct but the rest of the statement is not correct.

You will see why it is not correct if you consider m2. Is not m2 accelerating upwards?

 

[zzinfinity]

Thanks! got it.