Q in dynamics, kinetics, Energy

[vemplord]

Homework Statement

1 Kg block slides on a circular rod (no friction) from rest in A position by a force of 40N. What is the speed when it reached point B. (see attached pic)

Homework Equations

W(f)=E(B)-E(A)

The Attempt at a Solution

The energy in A is 0, the energy in B is mgh+0.5mv^2
My problem is how to find the work of the force.

Thx.

 

[tiny-tim]

Welcome to PF!

Hi vemplord! Welcome to PF!

(try using the X² tag just above the Reply box )

My problem is how to find the work of the force.

Work done = force "dot" displacement …

so for a small angle dθ, find the displacement, "dot" it with the force, and then integrate.

 

[vemplord]

Thanks,

I tried that:
The Y displacement is rsinθ an X displacement is r-rcosθ, tried to integrate from "0" to "π/2" but it doesn't come out right.

What am i doing wrong?

 

[tiny-tim]

Thanks,

I tried that:
The Y displacement is rsinθ an X displacement is r-rcosθ, tried to integrate from "0" to "π/2" but it doesn't come out right.

What am i doing wrong?

dunno … show us!