8 Jordan has a twin sister, Kathy. Jordan weighs 36 kilograms, and Kathy weighs 30 kilograms.
Jordan and Kathy like to play on the swing set at
the park. Their father pushes each of them until
they are swinging to the same height. Which is
true about the forces at work?

A. Kathy applied more force to the swing set than
to Jordan.
B. Their father applied more force to Kathy than to
Jordan.
C. Their father applied less force to Kathy than to
Jordan.
D. Kathy applied more force to her father than to
Jordan.

What is the final velocity of the initial velocity of 25 and -50?

Aheat engine running backward is called a refrigerator if its purpose is to extract heat from a cold reservoir. the same engine running backward is called a heat pump if its purpose is to exhaust warm air into the hot reservoir. heat pumps are widely used for home heating. you can think of a heat pump as a refrigerator that is cooling the already cold outdoors and, with its exhaust heat qh, warming the indoors. perhaps this seems a little silly, but consider the following. electricity can be directly used to heat a home by passing an electric current through a heating coil. this is a direct, 100% conversion of work to heat. that is, 19.0 \rm kw of electric power (generated by doing work at the rate 19.0 kj/s at the power plant) produces heat energy inside the home at a rate of 19.0 kj/s. suppose that the neighbor's home has a heat pump with a coefficient of performance of 4.00, a realistic value. note: with a refrigerator, "what you get" is heat removed. but with a heat pump, "what you get" is heat delivered. so the coefficient of performance of a heat pump is k=qh/win. an average price for electricity is about 40 mj per dollar. a furnace or heat pump will run typically 200 hours per month during the winter. what does one month's heating cost in the home with a 16.0 kw electric heater? what does one month's heating cost in the home of a neighbor who uses a heat pump to provide the same amount of heating?

What component of earth’s atmosphere exists entirely as a result of photosynthesis?