On a saturday afternoon, you decide to pay a neighborhood kid to mow your lawn. the kid uses a manual push lawn mower with a mass of m=12 kg. the handle of the lawnmower is tilted θ=37 degrees above the horizontal and the coefficient of kinetic friction between the lawnmower and the ground is μk=0.16. assume that the kid is pushing parallel to the handle. a. find an expression for much power the kid supplies to the lawnmower (pkid ) if the lawnmower is moving at a constant speed of 1.5 m/s? assume the kid is pushing parallel to the handle.

Conventional hot-water heaters consist of a tank of water maintained at a fixed temperature. the hot water is to be used when needed. the drawback is that energy is wasted because the tank loses heat when it is not in use, and you can run out of hot water if you use too much. some utility companies are encouraging the use of on-demand water heaters (also known as flash heaters), which consist of heating units to heat the water as you use it. no water tank is involved, so no heat is wasted. a typical household shower flow rate is 2.50 gal/min (9.46 l/min ) with the tap water being heated from 51.0 ˚f (10.6 ˚c) to 120 ˚f (48.9 ˚c) by the on-demand heater. what rate of heat input (either electrical of from gas) is required to operate such a unit, assuming that all the heat goes into the water?