PHYSICS · Multi-part · A Level · Physics · Mechanics and materials · Mechanics and materials
Problem
A 5.0 kg crate slides at 2.5 m s^−1 on a long, level warehouse floor that has a coefficient of kinetic friction of 0.10. Directly ahead, a 3.0 kg crate rests motionless on the same floor. The moving crate collides with the stationary one; the two crates latch together by means of a built-in hook and loop and then slide as a single object until coming to rest.
(a) Determine the speed of the joined crates immediately after the collision, taking the positive direction to be the direction of the original motion of the 5.0 kg crate.
(b) The crates slide to a stop after traveling a measured distance of 1.6 m. Using this information, calculate the coefficient of kinetic friction that acted on the joined crates during the sliding phase.
(c) Compare the coefficient found in part (b) with the stated floor value of 0.10. Provide at least one plausible physical explanation if the two values differ.
(d) Suppose instead that the floor were perfectly smooth (frictionless). Predict quantitatively how the distance required for the joined crates to come to rest would change, and justify your reasoning based on energy considerations.