Acceleration

Answer Key - Grade 11 Science Worksheet - Challenge Me

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

1. 1.

   East is positive. A cart starts at 2 m/s, accelerates at 3 m/s² for 4 s, then at -5 m/s² for 3 s. What is its final velocity, Ari?

   -1 m/s
2. 2.

   East is positive. A cart starts at 10 m/s, accelerates at -2 m/s² for 3 s, then at -4 m/s² for 5 s. What is its final velocity, Esme?

   -16 m/s

3. Read this first

   Three carts, velocity in m/s each second (example data)

   time (s)	cart A	cart B	cart C
   0	2	0	10
   1	4	1	7
   2	6	4	5
   3	8	9	4

4. 3.

   In the three-cart table, which cart has a constant acceleration over the 3 s, Jun?

   • Cart A, which gains 2 m/s every second
   • Cart B, which changes the most overall
   • Cart C, which changes every second
   • All three, since each velocity changes
5. 4.

   Two cars travel at 25 m/s, 30 m apart. The lead car brakes at 6.0 m/s²; the driver behind reacts after 0.70 s and brakes the same. Do they collide, Kira?

   • Yes: the follower needs 69.6 m but 30 m is free
   • Yes: the 0.70 s delay uses up the whole 30 m gap
   • No: both brake equally, so the gap stays 30 m
   • No: the gap shrinks by 17.5 m, leaving 12.5 m
6. 5.

   A rocket sled goes from rest to 80 m/s over 400 m at constant acceleration. What are a and the time taken, Luz?

   • a = 8.0 m/s²; t = 10 s
   • a = 8.0 m/s²; t = 5.0 s, from 400 ÷ 80
   • a = 0.20 m/s²; t = 400 s, from 80 ÷ 400
   • a = 16 m/s²; t = 5.0 s, dropping the factor 2
7. 6.

   A town says cutting the limit from 50 to 40 km/h cuts total stopping distance by only 20%. With 0.75 s reaction time and 6.0 m/s² braking, judge it, Milo.

   • Understated: the total falls about 30%, from 26.5 m to 18.6 m
   • Understated: it falls 36%, the braking part alone
   • Overstated: it falls 10%, since reaction time is fixed
   • Correct: 20% less speed means 20% less distance
8. 7.

   Noah says a ball falling at a steady 12 m/s in air has a = 0, so gravity has stopped acting. Judge the claim.

   • Wrong: a steady speed means that the ball is at rest
   • a = 0 is right, but gravity still acts; drag balances it
   • Wrong: a must stay 9.8 m/s² for as long as gravity acts
   • Right: a = 0 means that no force is acting on the ball
9. 8.

   Pia says a sprinter's average acceleration over 10 s, 1.06 m/s², shows how the sprinter speeds up. The sprinter reaches 10 m/s at 2 s and 10.6 m/s at 10 s.

   • Misleading: a was 5 m/s² early and under 0.1 m/s² later
   • Misleading: a was 1.06 m/s² early and 5 m/s² later
   • Fine: an average describes each second of the race
   • Fine: 1.06 m/s² lies between 0 and 10 m/s
10. 9.

    Constant a: a cart reads +6 m/s at t = 1 s and −4 m/s at t = 5 s. When does it turn around, Ren?

    • At t = 3.4 s, 2.4 s after the +6 m/s reading
    • At t = 2.4 s, counting from the clock's zero
    • At t = 5 s, the last reading
    • At t = 3 s, halfway between the readings

11. Braking tests (example data)

    speed (m/s)	distance to stop (m)
    10	8
    15	18
    20	32

12. 10.

    Using the braking table, what is the car's constant deceleration, and how far does it need from 30 m/s, Tala?

    • a = 12.5 m/s²; 36 m, dropping the factor 2
    • a = 6.25 m/s²; 48 m, scaling the distance with speed
    • a = 1.25 m/s²; 72 m, from 10 ÷ 8
    • a = 6.25 m/s²; 72 m from 30 m/s