Physics - Problem Solving
Work and Energy

1. An automobile of mass 1200 kg has a speed of 30 m/s on a horizontal road when the engine is developing 37300 Watts (50.0 horsepower). What is the speed, with the same power output, if the automobile now climbs a hill inclined at 30^o?

2. In the early 1980's, the total consumption of electrical energy in the U.S. was on the order of 1 X 10¹⁹ joules per year.
a) What was the average rate of energy consumption in watts? kilowatts?
b) If the population of the U.S. was 200,000,000, what was the average rate of energy consumption per person?
c) If the sun transfers energy to the earth by radiation at a rate of 1.4 kW per square meter of surface, how great an area would be required to collect the energy cited above?

3. The human heart is a powerful and reliable pump. Each 24 hour day, it takes in and discharges over 7500 liters of blood. If the work done by the heart is equal to the work required to lift this amount of blood a height equal to the average American female (1.63 m), and if the density of blood is the same as that of water,
a) how much work does the heart do in a day?
b) what is the power output in watts? horsepower?

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