Stored (potential) energy

Answer Key - Grade 8 Science Worksheet

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

1. 1.

   Ari carries a 0.5 kg water bottle up to a balcony 6 m above the ground. With g = 10 N/kg, how much stored energy does it gain?

   30 J
2. 2.

   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
3. 3.

   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
4. 4.

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

   • Doubling the mass or the height
   • Raising it higher, since mass does not count
   • Painting it a darker color
   • Making it roll faster
5. 5.

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

   • The same both times
   • At 20 cm
   • Neither, since it is held still
   • At 10 cm, since it is easier to hold
6. 6.

   Noah holds two attracting magnets 2 cm apart, then 6 cm apart. When do they store more energy?

   • At 2 cm, since the pull is stronger
   • At 6 cm
   • The same at both
   • Neither, while held still
7. 7.

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

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

9. Read this first

   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.

10. 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
    • 4 J of motion energy
    • 2 J of motion energy
11. 10.

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

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