Newton's Third Law question(a little help please)?

Question

There is a wedge with mass m2 with angle theta, and another mass m1 on the slope of the wedge. There is a force F being exerted on the wedge from the flat side. Find an expression for the magnitude of the horizontal force F in the figure for which m1 does not slip either up or down along the wedge. All surfaces are frictionless.

Answer 1

Wow, nice question for freshmen :)

First, we need an upward force of m1*g on m1. For this, we need (with some trigonometry) a total force (normal force) of

m1*g/cos(theta)

such a force exerts a horizontal force of

m1*g*sin(theta)/con(theta)=m1*g*tan(theta)

on m1, resulting in an acceleration of g*tan(theta). since the block does not slide up or down, we now know the acceleration of the system.

thus, F=(m1+m2)*a,
and, F= (m1+m2)*g*tan(theta)

There you are...

Answer 2

Google baby.