Speed, velocity and distance-time graphs

Answer Key - Grade 8 Science Worksheet - Building Confidence

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

1. 1.

   Ari graphs a scooter rolling at a steady speed. Use the two marked points. What is the scooter's speed?

   4 m/s
2. 2.

   Bo rolls a ball along a track and graphs it. Use the two marked points. What is the ball's speed?

   5 m/s
3. 3.

   Esme's toy car rolls at a steady speed across the gym. Use the two marked points. What is the car's speed?

   6 m/s
4. 4.

   Both runners keep a steady pace. Jun times two runners and lists their distances from the start. Which statement does the table support?

   • The runners cannot be compared, because they began at different distances from the start
   • Runner A is faster: its distance grows 4 m each second, while B's grows 2 m each second
   • The two runners have the same speed: both distances keep growing at a steady rate
   • Runner B is faster: its distance from the start is larger than A's at each time listed
5. 5.

   Distance is measured from the start line. Kira tracks two carts, one moving toward the start line and one moving away. Which cart has the greater speed?

   • The carts cannot be compared, since one moves toward the line and the other moves away
   • Cart E: its distance changes 5 m each second, while cart F's distance changes 3 m each second
   • The two carts have the same speed: both distances change by a steady amount each time they are read
   • Cart F: the distance of cart E is going down, which means cart E is hardly moving
6. 6.

   East is positive. Cart R has a velocity of −5 m/s and cart T has a velocity of +3 m/s. Which cart has the greater speed, Noah?

   • Cart T: +3 is a greater number than −5, so cart T has the greater speed
   • Cart R: its speed is 5 m/s, and the minus sign only shows that it moves west
   • Neither: the carts move in opposite directions, so their speeds cannot be compared
   • Cart T: a cart moving east is faster than a cart moving west, at any speed

7. Read this first

   Toy helicopter (example data)

   time (s)	height (m)
   0	10
   2	16
   4	12
   6	6

8. 7.

   Up is positive. Pia flies a toy helicopter. What is its velocity from 4 s to 6 s?

   • +6 m/s: the helicopter climbed 6 m between the first two readings, so that is its velocity
   • −6 m/s: the height falls by 6 m between the two readings at 4 s and 6 s
   • +3 m/s: the height changes by 3 m each second, so the helicopter rises
   • −3 m/s: the helicopter descends 3 m each second, so its velocity is negative
9. 8.

   Ren walks 30 m east to a mailbox, then 30 m back west to the start, in 40 s. Which description is correct?

   • Distance 60 m, displacement 60 m, average speed 1.5 m/s
   • Distance 60 m, displacement 0 m, average speed 0 m/s
   • Distance 0 m, displacement 0 m, average speed 0 m/s
   • Distance 60 m, displacement 0 m, average speed 1.5 m/s
10. 9.

    Tala runs one 400 m lap of a track in 80 s and ends back at the start. Which statement is true?

    • The displacement is 400 m, so the average velocity is 5 m/s in the direction of the run
    • The average speed is 0 m/s, since the runner ends at the starting line
    • The average speed is 5 m/s, but the average velocity is 0 m/s
    • The average speed and the average velocity are both 5 m/s
11. 10.

    Zee bikes 50 m north, then 20 m south, along a straight street. What is the bike's displacement?

    • 50 m north, the length of the first part of the ride, not the net change
    • 20 m south, the length of the last part of the ride, not the net change
    • 30 m north, the net change from the start of the ride to its end
    • 70 m north, the total length of the whole path of the bike