Electrical power companies sell electrical energy by the kilowatt-hour, where 1 kWh = 3.6x106 J.
Suppose that it costs $0.15 per kWh to run your
electric water heater. How much does it cost to heat
75 kg of water from 15°C to 43°C to fill a bathtub?

Emmy kicks a soccer ball up at an angle of 45° over a level field. she watches the ball's trajectory and notices that it lands, two seconds after being kicked, about 20 m away to the north. assume that air resistance is negligible, and plot the horizontal and vertical components of the ball's velocity as a function of time. consider only the time that the ball is in the air, after being kicked but before landing. take "north" and "up" as the positive ‑ and ‑directions, respectively, and use ≈10 m/s2 for the downward acceleration due to gravity.