A 19.0 kg child on a 1.00 m long swing is released from rest when the ropesof th

Question

A 19.0 kg child on a 1.00 m long swing is released from rest when the ropesof the swing make an angle of 26.0°with the vertical.
(a) Neglecting friction, find the child's speedat the lowest position.

(b) If the speed of the child at the lowest position is1.20 m/s, what is the mechanical energylost due to friction?
I think I'm on the right track, but I justcan't find the right equation! Thanks for help--Needed as soon aspossible, please! (a) Neglecting friction, find the child's speedat the lowest position.

(b) If the speed of the child at the lowest position is1.20 m/s, what is the mechanical energylost due to friction?
I think I'm on the right track, but I justcan't find the right equation! Thanks for help--Needed as soon aspossible, please!

Explanation / Answer

a. Applying the law of conservation of energy we have The change in PE at the =260 =change in KE atthe bottom mg(h-hcos26)=1/2*m(v12-v22) g*1(1-cos26)=1/2*(v2-0) v=2*9.8(0.1) v=1.4m/s b. The mechanical energy lost is E=1/2*19*1.42-1/2*19*1.22 E=4.94J E=4.94J

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