A baseball (m = 140 g) approaches a bat horizontally at a speed of 39.7 m/s (89 mi/h) and is hit straight back at a speed of 45.5 m/s (102 mi/h). If the ball is in contact with the bat for a time of 1.05 ms, what is the average force exerted on the ball by the bat? Neglect the weight of the ball, since it is so much less than the force of the bat. Choose the direction of the incoming ball as the positive direction.

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?