Well here are 5 questions from my text which I've tried doing but can't seem to twist my ahead around to figure them out. I don't know if it's due to the fact that I'm not applying the relevant concepts. Thanks for any help. (1). A uniform cord of length 25cm and mass 15g is initally stuck to the ceiling. Later, it hangs vertically from the ceiling with only one end still stuck. What is the change in gravitational potrntial energy of the cord with the change in oreintation? (All I know is that this question involves the use of calculus and that's something which I would like someone to help me sort out.) (2). Two children are playing a game in which they try to hit a small box on the floor with a marble fired from a spring-loaded gun that is mounted on a table. The target box is a horizonatal distance D = 2.20m from the edge of the table. Bobby compresses the spring 1.10cm but the centre of the marble falls 27.0cm short of the centre of the box. How far should Rhonda compress the spring to score a direct hit, assuming that neither the spring nor the ball encounters friction in the gun? (3). A cable of a 1800kg elevator cab snaps when the cab is at rest at the first floor, where the cab is 3.7m above a spring of spring constant k = 0.15MN/m. A safety device clamps the cab against guide rails so tha a constant frictional force of 4.4 kN opposes the cab motion. (a) Find the speed of the cab just before it hits the spring (b) Find the maximum distance x that the spring is compressed (the frictional force still acts during the compression) (c) Find the distance that the cab will bounce back u the shaft (d) Using the conservation of energy, find the approxiamate total distance that the cab wil move before coming to rest. (assuming that the frictional force on the cab is negligible when the cab is stationary) (4). A metal soda can of uniform composition has a mass of 0.140kg and is 12.0cm tall. This can is filled with 1.31kg of soda then small holes are drilled into the bottom (with negligible loss of metal) to drain the soda. What is the height h of the centre of mass of the can and contents (a) intially and (b) after the can loses all of the soda (c) What happens to h as the soda drains? (d) If X amount remains in the soda at a given instant, what is X when the centre of mass is at its lowest point? (5). A ball of mass 300g with a speed of 6.0m/s strikes a wall at an angle of 30 degrees and then rebounds with the same speed and angle. It is in contact with the wall for 10 ms. In unit vectors, what are (a) the impulse on the ball from the wall and (b) the average force on the wall from the ball?