1) If a planet moves in a circle about the sun, how much work does the force of gravity do on the earth? Give reasons for your answer.
2) A force of 120N pushes a crate mass 15kg along the ground at a constant speed of 3.2 m/s for a distance of 6.2m. What amount of heat energy was generated at this time?
3)The earth has a mass of 5.98 x10^24 kg and a speed of 2.97 m/s. The sun, which is 1.49 x10^11m away, exerts 3.56 X10^11 N on it. If the earth orbited the sun in a perfect circle, how much work would the sun do on the earth in one second?
4) A car of mass 1350kg rolls from rest down a hill 235m long and 25m high. If its speed at the bottom of the hill is 12.0m/s, what's the force of friction on the car?
The Attempt at a Solution
1) I said none because the disatnce in the equation force times distance has to be a parallel distance to the force exerted on it, and its not in this case.
(3.56 x10^11 N)(2.97m)=1.06 x10^12 J
W= 330750-97200=233550 J