A uniform 1.0 m long rod of mass 2 kg rests on a frictionless horizontal surface
PHYSICS · Single correct · A Level · Physics · Engineering physics · Engineering physics
Problem
A uniform 1.0 m long rod of mass 2 kg rests on a frictionless horizontal surface. A brief horizontal impulse of 3 N·s is delivered perpendicular to the rod at one of its ends. A student models the rod as if all its mass were concentrated at its center to predict its subsequent motion. Which of the following observed outcomes would most clearly indicate that this point-mass model is inadequate?
(a) The rod’s center of mass moves more slowly than the predicted 1.5m/s, while the rod simultaneously rotates about its center.
(b) The rod’s center of mass moves with the predicted speed, but the rod also begins to rotate about its center.
(c) After the impulse, the rod’s speed keeps increasing—indicating a continuous acceleration beyond the predicted value.
(d) The rod’s center of mass moves with the predicted speed, but the rod appears to rotate about the struck end rather than about its center.