A sled and rider with a combined weight of 56 kg are at rest on the top of a hil

Question

A sled and rider with a combined weight of 56 kg are at rest on the top of a hill 23 m high. (a) What is their total energy at the top of the hill? J (b) Assuming there is no friction, what would the total energy be on sliding halfway down the hill? J A student who weighs 570 N climbs a stairway (vertical height of 2, 8 m) in 29 s. (a) How much work is done? J (b) What is the power output of the student? W on a particular day, the following appliances are used for the times indicated: a 1600-W coffee maker, 17 min, and a 1100-w microwave oven, 4.1 min, With these power requirements, find how much it costs to use these appliances at an electrical cost of 7c per kWh. (Do not round your final answer, Fractional cent values are acceptable.)

Explanation / Answer

7.a) Total energy at top= mgh =56x9.8x23 J=12622.4 J

This is only potential energy.

B) Energy conservation implies total energy at midway will be equal to total energy at top =12622 J.

But there will be both kinetic and potential energy.

8. a) Work =Force x displacement =570 x2.8 J =1596 J

b)Power =work /time =1596 /29 Watt =55.034 Watt

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