PHYSICS · Multi-part · A Level · Physics · Mechanics and materials · Mechanics and materials
Problem
A skier on a straight, level track undergoes a three-stage motion before coming to rest at a lodge located farther down the track.
• Stage 1: Starting from rest, the skier accelerates uniformly for 30s until reaching a speed of 12ms−1.
• Stage 2: The skier then maintains this speed for 60s.
• Stage 3: Finally, the skier decelerates uniformly to rest in 15s.
Neglect friction and air resistance.
(a) Determine the displacement of the skier during each of the three stages.
(b) Calculate the skier’s total displacement for the entire trip from the starting point to the lodge.
(c) Using your answer from part (b) and the total elapsed time, compute the skier’s average velocity for the trip and indicate its direction along the track.
(d) Compare the magnitude of the average velocity you found in part (c) with the maximum speed attained during Stage 1, and explain physically why the two values differ.