Displacement and velocity, with a frame of reference

Answer Key - Grade 11 Science Worksheet - Building Confidence

Circle the best answer, or write your answer on the line.

1. 1.

   East is positive. Ari's cart goes from x = -8 m to x = 14 m in 11 s, rolling 40 m in all. What is its average velocity?

   2 m/s
2. 2.

   East is positive. Bo's cart goes from x = 12 m to x = -6 m in 9 s, rolling 30 m in all. What is its average velocity?

   -2 m/s
3. 3.

   In the position-time graph, a cart moves from x = 12 m to x = 0 m in 6 s. What is its velocity, Jun?

   • 12 m/s, the starting position
   • −2 m/s: it moves toward the origin
   • 0 m/s, since it ends at the origin
   • +2 m/s, since a speed cannot be negative
4. 4.

   In the position-time graph, the lines for carts A and B cross at 5 s. What is true at that moment, Kira?

   • The same speed, so the same velocity of 2 m/s
   • Same place and the same velocity, since the lines meet
   • Same place, equal speeds, opposite velocities (+2 and −2 m/s)
   • Both carts stop, since they reach the same place
5. 5.

   East is positive. Luz's cart rolls from x = −4 m to x = 9 m, then back to x = 2 m. What are its displacement and total distance?

   • Displacement +2 m; distance 20 m
   • Displacement +6 m; distance 6 m
   • Displacement 20 m; distance 20 m
   • Displacement +6 m; distance 20 m
6. 6.

   East is positive. Train A moves +30 m/s and train B moves +24 m/s on parallel tracks. What is B's velocity as seen from A, Milo?

   • 54 m/s toward the east
   • 6 m/s toward the east
   • 24 m/s toward the east, its ground velocity
   • 6 m/s toward the west
7. 7.

   East is positive. A river flows +3 m/s. Noah paddles west at 5 m/s relative to the water. What is the boat's velocity relative to the bank?

   • 2 m/s toward the west
   • 2 m/s toward the east
   • 8 m/s toward the west
   • 5 m/s toward the west, the paddling speed
8. 8.

   A runner completes one 400 m lap in 80 s and ends where it started. What are the average speed and average velocity, Ren?

   • Speed 5 m/s; velocity 5 m/s
   • Speed 0 m/s; velocity 0 m/s
   • Speed 5 m/s; velocity 0 m/s
   • Speed 0 m/s; velocity 5 m/s
9. 9.

   In the position-time graph, what is the cart's velocity from 0 to 3 s, then from 3 to 6 s, Tala?

   • 0 m/s, then +6 m/s, the rise alone
   • 4 m/s, then +2 m/s, treating flat as steady motion
   • 0 m/s, then +2 m/s
   • 4 m/s, then 10 m/s, the positions
10. 10.

    East is positive. Zee's cart moves from x = −6 m to x = −2 m in 2.0 s. Which statement is true?

    • Its velocity is −2 m/s, since its position is negative
    • Its velocity is +4 m/s, the displacement
    • Its velocity is +2 m/s: it moves west, away from the origin
    • Its velocity is +2 m/s: it moves east, toward the origin