Acar is traveling with a velocity of 35.4 m/s. the mass of the car is 2000 kg. what is the momentum of the car? and can you explain how to figure this out?
the choices are:

a. 65.5 kg×m/s
b. 70,800 kg×m/s
c. 78,000 kg×m/s
d. 56.5 kg×m/s

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?