Motion (kinetic) energy, and how mass and speed change it

Answer Key - Grade 8 Science Worksheet

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

1. 1.

   Ari and the bike have a mass of 50 kg and ride at 4 m/s. What is the motion energy?

   400 J
2. 2.

   Bo's 3 kg skateboard rolls across the park at 4 m/s. What is the motion energy?

   24 J
3. 3.

   Esme kicks a 0.5 kg ball, and it rolls at 6 m/s. What is the motion energy?

   9 J
4. 4.

   Jun doubles the speed of a scooter, with the same rider. What happens to its motion energy?

   • It doubles
   • It stays the same as it was before
   • It becomes four times as much
   • It halves
5. 5.

   Kira rolls a cart three times as fast as before. How does its motion energy change?

   • Six times as much
   • Nine times as much
   • The same
   • Three times as much
6. 6.

   Luz slows a bike to half its speed. How does its motion energy change?

   • It becomes half
   • It becomes one quarter
   • It does not change
   • It becomes double
7. 7.

   A wagon carries twice the load at the same speed. How does its motion energy change, Milo?

   • The same, since speed decides it
   • Four times as much
   • Twice as much
   • Half as much
8. 8.

   Noah compares a 1 kg ball and a 3 kg ball rolling at the same speed. The 3 kg ball has…

   • one third the motion energy
   • three times the motion energy
   • the same motion energy
   • nine times the motion energy
9. 9.

   Cart A is 2 kg moving at 4 m/s. Cart B is 4 kg moving at 2 m/s. Which has more motion energy, Pia?

   • Cart B, since it is heavier
   • Cart A
   • Cart B, since mass counts double
   • The same, since 2 × 4 = 4 × 2
10. 10.

    Tala coasts a bike up a hill until it stops. What happened to the 800 J of motion energy?

    • It went into the air as wind
    • It stayed as motion energy
    • It was used up by the hill
    • It became stored energy from height