1.1. You drop a ball from a height of 2m above the ground. Describe what happens to its potential energy, kinetic energy, and total energy as the ball falls towards the ground. 2. Estimate (to the nearest order of magnitude) how much work I must do to pick up a 12 kg box to a height of 1.3m. Does it mattert how I pick up the box (fast or slow, straight up or along a curvy path, etc.)? 3. In which of the following cases do I do positive work on a ball? I pick up a ball from the ground to a height of 1.4m I slowly set a ball down from a height of 1.4m down onto the ground. I hold a ball still at height 1.4m. Two of the above All of the above 4. Explain your answer to the multiple choice question above. 2.U=mgy W(grav)=U(i)-U(f) 3. 1. The potential energy is the highest at the top (2m above the ground) because that is when it is highest. As it falls and picks up speed, though, the potential energy gets transfered into kinetic energy, and kinetic energy increases, and potential energy decreases. The total energy, though, is the same throughout the process. 2. 12*9.8*1.3=152.88 J (nearest order of magnitude 150 J) It doesn't matter how you pick up the box, as long as the displacement is the same. For the gravitational work, it doesn't matter how fast or slow you pick up the box, but for total work, where kinetic energy is included, then, the difference between starting and ending velocities would be important. 3. I slowly set a ball down from a height of 1.4m down onto the ground. 4. "I slowly set the ball down from a height of 1.4m down onto the ground" is the only option that includes reducing the height, which would cause the gravitational potential energy to decrease, and for gravitational force to do positive work on the ball. Thanks for the help guys!!!