Verify Answers to Mechanical Energy Homework

[goonking]

Homework Statement

You do 100 J of work while pulling a child back on a swing, whose chain is 2.0 m long, until the swing makes an angle of 30.0° with the vertical. a) What is the child's mass? (Consider the swing itself and the chain massless) b) Upon releasing the swing from this position, what will the speed of the child be at the bottom of the arc?

Homework Equations

mgh = 1/2 mv^2

The Attempt at a Solution

After doing some trig, I get the height difference of the swing to be 0.267m; we now have h in mgh.

since he exerted 100 Js, we set mgh = 100, solving for m

m = 38.21 kg

now we want to find the speed at the bottom of the arc.

we set mgh = 1/2 mv^2

Mass cancels out

we solve for V, which should be 2.287 m/s.

Can someone verify if my answers are correct?

 

[TSny]

Your work looks good to me.