Question

2.3 position vs. time graphs

1. a hockey puck is shot down the arena in a straight line. assume it does not slow until it is stopped by an opposing player who sends it back in the direction it came. the players are 20 m apart and it takes 1 s for the puck to go there and back. which of the following describes the graph of the displacement over time? consider the initial direction of the puck to be positive.

a. the graph is an upward opening v.
b. the graph is a downward opening v.
c. the graph is an upward opening u.
d. the graph is downward opening u.

Explanation:

Step1: Analyze the motion

The puck moves forward in the positive - direction with a constant speed, then changes direction and moves back in the negative - direction with a constant speed.

Step2: Consider displacement - time relationship

Displacement is a vector quantity. When moving forward, displacement increases linearly with time. When moving back, displacement decreases linearly with time.

Step3: Determine the shape of the graph

The graph of displacement vs time will have a constant positive slope for the forward journey and a constant negative slope for the return journey, forming a downward - opening V - shaped graph.

Answer:

b. The graph is a downward opening V.