need some help on these problem Name Date Partners HOMEWORK FOR LAB 5: CONSERVAT
ID: 1290821 • Letter: N
Question
need some help on these problem
Name Date Partners HOMEWORK FOR LAB 5: CONSERVATION OF ENERGY 1. A ball of mass 5.0 kg is lifted off the floor a distance of 1.7 m. What is the change in the gravitational potential energy of the ball? Show your calculation. Answer: J 2. Now the ball is released from rest and falls to the floor. What is the kinetic energy of the ball just before it hits the floor? What is its velocity? Show your answers. Answers: kinetic energy: rest and falls to the floor. velocity: ms 3. Suppose that the ball is dropped from the same height as in Question 2, but is attached to a parachute. Compare the kinetic energy just before the ball hits the floor to your answer in Question 2. Is it the same, larger, or smaller? Is mechanical energy conserved in this case? Explain your answer. 4. A ball is tossed in the air and released. It moves up, reverses direction, falls back down again, and is caught at the same height it was released. a. Considering the time interval after the ball is released and before it is caught, when does the gravitational potential energy of the ball have its maximum value? Minimum value? Explain. b. When does the kinetic energy of the ball have its maximum value? Minimum value? Explain. c.What about the mechanical energy of the ball? What can you say about its value at the locations described in your answers to (a) and (b) ?Explanation / Answer
1) P.E.=mgh
=(5kg)(9.81m/s^2)(1.7m)
PE= 83.385 J
2)Total PE at the top =KE on the bottom
so, KE=PE therefore, KE= the PE found in part 1
KE=83.385 J
KE=1/2 mv^2
83.385 J=1/2 *5*v^2
v^2=33.354
v=5.775m/s
3) it is smaller, there is not as much total force acting on the ball (in other words work due to air resistance opposing gravitational work)
4)A. The ball has maximum gravitational potential energy at the top, minimum (zero) at the bottom. GPE is mass * g * height.
B. Kinetic energy is proportional to the square of the speed. It is maximum at the bottom, and minimum (zero) at the top.
C. The total energy during the ball's travel, kinetic and potential, is constant. On the way up, kinetic energy gets converted to potential, and on the way down the conversion of energy goes in reverse.
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