A closed glass cabin of negligible mass is kept on a perfectly smooth horizontal ice…
PHYSICS · Subjective · A Level · Physics · Mechanics and materials · Mechanics and materials
Problem
A closed glass cabin of negligible mass is kept on a perfectly smooth horizontal ice surface. A student of mass 70kg stands inside the cabin and the whole system is initially at rest with respect to the ground.
(i) Define an isolated system.
(ii) Taking the student–cabin combination as the system, explain whether it is isolated while the student is standing still.
(iii) The student now walks briskly from the rear wall towards the front wall of the cabin with a speed of 1ms−1 relative to the cabin floor. Identify all the forces acting during the walk and classify each as internal or external to the chosen system.
(iv) Will the linear momentum of the student–cabin system about the ground remain conserved during the walk? Give a detailed reason referring to the forces identified in part (iii).