Two figure skaters, Skater A of mass and Skater B of mass
PHYSICS · Multi-part · A Level · Physics · Mechanics and materials · Mechanics and materials
Problem
Two figure skaters, Skater A of mass 55kg and Skater B of mass 75kg, stand facing each other on frictionless ice. They initially form a closed system at rest with respect to the ice. While holding a lightweight rope, they use only internal forces to pull themselves closer and then push off so that they separate and glide apart along a straight line.
(a) Describe qualitatively the motion of the center of mass of the two–skater system during the entire interaction, from the moment they start pulling on the rope to long after they have pushed off and are gliding freely.
(b) Explain your answer to part (a) by referring to the presence or absence of external forces acting on the system.
(c) As the skaters pull together, which skater moves through the greater distance before they make contact? Justify your answer without using numerical calculations.
(d) After the push-off, Skater A is observed to glide eastward at 2.4m⋅s−1. Without performing a calculation, state whether Skater B’s speed is greater than, less than, or equal to 2.4m⋅s−1 and justify your reasoning.