Question based on laws of motion (inclined motion )

[Abhishek_R]

Homework Statement

what is the value of F needed so that block begins to move upward on frictionles incline plane .

Homework Equations

The Attempt at a Solution

i made an attemp and got the answer - Mgtan(thetta)
but the real answer is - mgtan(thetta/2)

 

[gneill]

Hi Abhishek_R, Welcome to Physics Forums.

You'll have to describe your problem more clearly: How (in what direction) is the force F applied? How is the angle $\theta$ defined?

Did you draw a Free Body Diagram? Show us the work you did on your attempt.