A box weighing 4 lbs. is on a frictionless surface in circular motion with a radius of 2 ft. from the center post and a tangential velocity of 5 ft/sec. Suddenly at point A the rope holding the box to the post starts to be retracted at a velocity of 4 ft/sec. What is the speed of the box at point B, where the radius has reduced to 1 ft.? After pulling the rope in from A to B, how much work was done? You may neglect the mass of the rope and the size of the box.

The roller coaster from problem #1 then tops a second hill at 15.0 m/s, how high is the second hill? 91.5 m 79.2 m 80.0 m 68.5 m

Consider an ordinary, helium-filled party balloon with a volume of 2.2 ft3. the lifting force on the balloon due to the outside air is the net resultant of the pressure distribution exerted on the exterior surface of the balloon. using this fact, we can derive archimedes’ principle, namely that the upward force on the balloon is equal to the weight of the air displaced by the balloon. assuming that the balloon is at sea level, where the air density is 0.002377 slug/ft3, calculate the maximum weight that can be lifted by the balloon. note: the molecular weight of air is 28.8 and that of helium is 4.

The table below shows the acceleration of gravity on different bodies in the solar system. on which body would a 10 kg lamp has the most gravitational potential energy when lifted to a height of 2 m? a. earth b. mars c. neptune d. uranus