Gain/Loss of Kinetic/Potential Energy of Pulley System

[reggie]

Two blocks are connect by a lght string which passes over a light pulley as shown in the figure. They are released from rest. Block A distance of 1.2m in 1.6 s
http://img149.exs.cx/img149/3595/pulley5uz.th.jpg
1. what is the gain in the kinetic energy of the two blocks?

2.What is the loss in potenial energy of the two blocks?

3.Explain why the two values in parts (1) and (2) differ.
A is 4 kg
B is 6 kg

 

[Davorak]

After finding the initial kinetic energy and the energy due to falling you should be able to find the speed at which it hits the planet.

Was this too much info?

Use kinematic equations to find the acceleration with the additional info "1.2m in 1.6 s." Use the acceleration and the time to find the final velocity. From the velocity you can find the kinetic energy.

You know how far block A has moved up and you know how for block b has moved down. Find the change in potential energy.

 

[thepatientmental]

1. The gain in kinetic energy of the two blocks can be calculated using the equation KE = 1/2mv^2, where m is the mass of the block and v is its velocity. In this case, block A has a mass of 4 kg and travels a distance of 1.2m in 1.6s, so its final velocity can be calculated as v = d/t = 1.2m/1.6s = 0.75m/s. Therefore, the kinetic energy of block A is KE = 1/2(4kg)(0.75m/s)^2 = 1.5J. Similarly, block B has a mass of 6 kg and travels the same distance in the same time, so its final velocity is also 0.75m/s and its kinetic energy is KE = 1/2(6kg)(0.75m/s)^2 = 2.25J. The total gain in kinetic energy for the two blocks is then 1.5J + 2.25J = 3.75J.

2. The loss in potential energy of the two blocks can be calculated using the equation PE = mgh, where m is the mass of the block, g is the acceleration due to gravity (9.8m/s^2), and h is the height from which the block is released. In this case, both blocks are released from rest, so their initial potential energy is PE = 0. Block A has a mass of 4 kg and falls a height of 1.2m, so its final potential energy is PE = (4kg)(9.8m/s^2)(1.2m) = 47.04J. Similarly, block B has a mass of 6 kg and falls the same height, so its final potential energy is PE = (6kg)(9.8m/s^2)(1.2m) = 70.56J. The total loss in potential energy for the two blocks is then 47.04J + 70.56J = 117.6J.

3. The values in parts (1) and (2) differ because they represent different forms of energy. Kinetic energy is the energy an object possesses due to its motion, while potential energy is the energy an object possesses due to its position or height above the ground. In this pulley system