PHYSICS · Multi-part · A Level · Physics · Mechanics and materials · Mechanics and materials
Problem
A hockey puck slides on nearly friction-free ice. Its linear momentum p along the +x axis is recorded at several instants; between the listed instants the momentum varies linearly with time.
Time t(s): 0.0 2.0 4.0 6.0 7.0
Momentum p(kg⋅m/s): 0.0 4.0 4.0 \!-2.0 \!-2.0
The sign of p indicates direction along the x-axis.
Answer the following questions about the net external force acting on the puck.
(1) Describe qualitatively the net external force during each of the four intervals 0–2 s, 2–4 s, 4–6 s, and 6–7 s. In your description include both magnitude (constant, increasing, zero, etc.) and direction (+x or –x).
(2) Explain how the sign of the slope of the momentum–time graph determines the direction of the net external force acting on the puck.
(3) Identify any interval(s) during which the net impulse delivered to the puck is zero and justify your answer using properties of the momentum graph.