A child starts at the top of a hill of height h = 9 m and sleds down as shown in

Question

A child starts at the top of a hill of height h = 9 m and sleds down as shown in the diagram. The mass of the child plus sled is 45 kg.

(a) If the child's speed just before she reaches the bottom of the hill is 2.2 m/s, what is the work done by non-conservative forces?

-3860.1 J

(b) The child and sled eventually come to a stop at location D. During the trip from location C to location D, the work done by friction forces between the ice and the sled is -64 J. What is the total energy of the child and sled at location C?

I got A, but I can't figure out part B!

Explanation / Answer

To do part (b): U know that the TOTAL mech energy at the top of the hill is totally GPE = mgh mgh here = (60)(9.81)(9) = 5297 J and U calculated the friction loss for the entire ride (down to pt D) = 5147 J and the prob states that 64 J was lost to friction in moving from C to D. so wouldn't U just take the TOTAL energy of sled&rider subtract the TOTAL loss due to friction U found in part (a) and ADD back the loss from pt C to pt D?

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