A student wearing frictionless roller skates (total mass
PHYSICS · Multi-part · CBSE · Physics · Laws of Motion · Laws of Motion
Problem
A student wearing frictionless roller skates (total mass, student plus skates, 60\,kg) is initially at rest on a level ice rink. The student holds a 0.40\,kg ball. Beginning at t=0s, the student exerts a horizontal force on the ball for 0.30\,s, throwing it forward (positive x-direction) at 12\,m/s relative to the ice. Air resistance is negligible, and the force exerted by the ice on the skates is vertical only.
(a) For the interval during which the force on the ball is exerted, consider the system consisting solely of the ball. Calculate the magnitude of the impulse delivered to the ball.
(b) For the same interval, consider instead the system consisting of the student plus skates. Determine both the magnitude and direction of the impulse experienced by this system.
(c) For the combined system of student, skates, and ball together, state and justify whether the net external impulse during the throwing interval is zero or non-zero.
(d) Using your results, determine the speed and direction of the student (with skates) immediately after the ball leaves the student’s hand.