Motion (kinetic) energy, and how mass and speed change it
Grade 8 Science Worksheet - Building Confidence
Circle the best answer, or write your answer on the line.
Ari's 4 kg skateboard rolls at 3 m/s. Use KE = ½ × m × v². What is its motion energy?
Bo's 8 kg wagon rolls at 3 m/s. Use KE = ½ × m × v². What is its motion energy?
Esme's 4 kg bowling ball rolls at 5 m/s. Use KE = ½ × m × v². What is its motion energy?
A 1 kg cart and a 2 kg cart roll at the same 2 m/s. Which has more motion energy, Jun?
- The same, since the speeds match
- The 1 kg cart, since it is easier to push
- The 2 kg cart
A bowling ball and a tennis ball roll at the same 4 m/s. Which has more motion energy, Luz?
- The tennis ball, since it bounces
- The same, since the speeds match
- The bowling ball
Milo's cart stops when its brake rubs the wheel. How much thermal energy is made?
- 20 J; half was lost
- 40 J
- 0 J; the energy was used up
Read this first
Use this
Energy bar chart (example data), one bar per energy store, height in J. Coasting: motion 600 J; thermal 0 J. Stopped: motion 0 J; thermal ?. A transfer arrow goes from motion to thermal, labeled brake pads.
Noah brakes a bike to a stop. Where did its 600 J of motion energy go?
- Nowhere; it ran out
- Back into the rider's legs
- Into thermal energy in the brakes
Use this
Energy bar chart (example data), one bar per energy store, height in J. Sliding: motion 90 J; thermal 0 J. Stopped on the snow: motion 0 J; thermal ?. A transfer arrow goes from motion to thermal, labeled friction with snow.
Pia's sled slides to a stop on flat snow. How much thermal energy is made?
- 45 J
- 90 J
- 0 J
Motion energy of a 2 kg cart (example data)
speed (m/s) motion energy (J) 1 1 2 4 3 9 Ren's table shows a 2 kg cart's motion energy. Each value is the speed times itself. What is it at 4 m/s?
- 16 J
- 12 J
- 8 J
Zee's cart has 9 J of motion energy at 3 m/s. Doubling the speed gives four times the energy. What at 6 m/s?
- 12 J
- 18 J
- 36 J