Stored (potential) energy

Answer Key - Grade 8 Science Worksheet

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

1. 1.

   Bo lifts a 6 kg backpack onto a hook 1.5 m above the floor. With g = 10 N/kg, how much stored energy does it gain?

   90 J
2. 2.

   Esme and a parent lift a 12 kg box of games into a loft 2.5 m up. With g = 10 N/kg, how much stored energy does it gain?

   300 J

3. Read this first

   Stored energy of a 2 kg ball (example data)

   height (m)	stored energy (J)
   1	20
   2	40
   3	60

4. 3.

   Jun's table shows a 2 kg ball at three heights. What would its stored energy be at 6 m?

   • 60 J, the most it can have
   • 80 J
   • 40 J, since it falls faster from higher
   • 120 J

5. Stored energy at a height of 2 m (example data)

   mass (kg)	stored energy (J)
   1	20
   2	40
   4	?

6. 4.

   Kira's table shows balls of different mass on the same 2 m ledge. How much does the 4 kg ball store?

   • 160 J
   • 40 J, the same as 2 kg
   • 20 J, since the height is the same
   • 80 J
7. 5.

   Luz wants a ball on a shelf to store twice as much energy. Which change works?

   • Painting it a darker color
   • Raising it higher, since mass does not count
   • Making it roll faster
   • Doubling the mass or the height
8. 6.

   Milo stretches the same exercise band 10 cm, then 20 cm, holding it still each time. When does it store more energy?

   • Neither, since it is held still
   • At 10 cm, since it is easier to hold
   • The same both times
   • At 20 cm
9. 7.

   Pia squeezes a jumping toy's spring 2 cm, then 5 cm. Which squeeze stores more energy?

   • The same, since it is one spring
   • 5 cm
   • 2 cm, since a small squeeze is quicker
   • Neither, since the toy is still
10. 8.

    Ren drops a ball from 2 m. Which bars fit halfway down?

    • Stored 0 J, motion 20 J
    • Stored 40 J, motion 40 J
    • Stored 20 J, motion 0 J
    • Stored 20 J, motion 20 J

11. Use this

    Energy bar chart (example data), one bar per energy store, height in J. Toy car at the top of the track: stored 2 J; motion 0 J. At the bottom: stored 0 J; motion ?. A transfer arrow goes from stored to motion, labeled rolling down. Friction and sound are small enough to leave out.

12. 9.

    Tala's toy car rolls down a track. Which describes its energy at the bottom?

    • No energy left; it was used to roll
    • Most stored energy, since it moves fastest
    • 2 J of motion energy
    • 4 J of motion energy
13. 10.

    Zee's class pulls a pendulum aside and lets go. What is true at the lowest point?

    • 10 J
    • 5 J of stored energy, since it is fastest
    • 5 J of motion energy
    • No energy, since the push is gone