Mary (mass = 33 kg) likes to slide too. On a nearby playground there is a straig

Question

Mary (mass = 33 kg) likes to slide too. On a nearby playground there is a straight metal slide with a vertical drop of 2.0 m and a length (measured along the slide) of 3.3 m. Suppose she starts from rest at the top of the slide and has a speed of 2.7 m/s when she reaches the bottom. (a) What was the net change in potential energy when she went from the top of the slide to the bottom? And what was the change in her kinetic energy? Be sure to indicate the correct signs (positive or negative). (b) What was the net change in the thermal energy of the slide and the seat of her pants due to friction between her pants and the slide? (Hint: this is simply the work done by friction

Explanation / Answer

a)change in PE=PEf-PEi=0-33*9.8*2=-646.8J
change in KEf-KEi=.5*33*2.7^2-0=120.285J
b)Wfriction=-PE-KE=526.515J
c)
N=mgcos
f=ukmgcos
cos=2/3.3
Wf=f*3.3=uk*33*3.3*9.8*2/3.3=526.515
=>uk=.814

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