A student conducts two trials in which a block is pulled with a light horizontal rope…
PHYSICS · Multi-part · A Level · Physics · Mechanics and materials · Mechanics and materials
Problem
A student conducts two trials in which a 1.0kg block is pulled with a light horizontal rope for 2.0m across a table.
• Trial 1: The surface is essentially friction-free, and the block is released after the pull so that it continues sliding.
• Trial 2: The same pulling motion is repeated, but the table now exerts a kinetic-friction force on the block that quickly brings it to rest before it has slid the full 2.0m once released.
Assume the pull is identical in magnitude and direction for the same 2.0m in both trials.
(a) Describe qualitatively how the total mechanical energy of the block changes during Trial 1 while the rope is pulling the block and after the rope is released. Explain your reasoning.
(b) In Trial 2 the block ends at rest. Explain what happened to the energy transferred to the block by the pulling force.
(c) Compare the magnitude of the work done by the student on the block in Trial 1 with that in Trial 2. Justify your comparison using energy considerations.