A pair of identical air-hockey pucks are taped together to form a single object that…
PHYSICS · Multi-part · CBSE · Physics · Laws of Motion · Laws of Motion
Problem
A pair of identical 0.25kg air-hockey pucks are taped together to form a single 0.50kg object that slides across a virtually frictionless table at 1.8m/s in the positive x-direction. At t=0s a brief external horizontal force acts on the taped pucks. The magnitude of the force as a function of time is represented by a rectangle: 3.0N directed opposite the motion (negative x-direction) and lasting for 0.15s. Immediately after the force ends, the tape connecting the pucks is cut without exerting any additional horizontal forces, leaving the pucks free but still in contact. The contact forces between the two pucks during the separation interval are internal to the two-puck system.
(a) Calculate the magnitude and direction of the impulse delivered to the taped pucks by the external force.
(b) Determine the speed and direction of the center of mass of the two-puck system immediately after the external force ends but before the tape is cut.
(c) Consider the very short interval during which the tape is cut and the pucks separate but remain on the frictionless table. For the system consisting of both pucks together, state and justify whether the net external impulse during this separation interval is zero or non-zero.
(d) Suppose instead that only the left puck is chosen as the system during the separation interval. Describe qualitatively the direction of the impulse this puck receives during separation and explain the physical origin of that impulse.