Leah watches a toy car move across a table at a constant speed. the car moves across the table in one direction and falls off the other side. leah decides to try another situation. she watches the car move across the table at a constant speed, then when it reaches the other side of the table, her friend joey pushes the car in the other direction. the car moves back to leah. based on leah's informal experiment, what forces cause the car to change direction? a. balanced forces from joey pushing the car b. unbalanced forces from joey pushing the car c. unbalanced forces from leah watching the car d. balanced forces from the car moving across the table

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?