PhysicsEnergy in Motion: Speed and Weight Both Count
Lumi the glowing lantern sprite cheers beside a sunny bowling lane, hoisting a heavy ball overhead and then rolling it with a big grin to scatter the wooden pins
- Identify that any object that is moving carries energy.
- Compare how a faster-moving object pushes harder than a slower one.
- Compare how a heavier moving object pushes harder than a lighter one moving at the same speed.
- Predict which moving object will knock something over with more energy.
Key terms
- motion energy
- the energy a moving thing carries
- speed
- how fast something is moving
- weight
- how heavy a thing is
- work
- using a push to move something
Faster Means More Energy
Anything that moves carries motion energy, and that energy can push things. Speed changes how much motion energy a thing has. Roll a ball slowly into some pins and they barely move. Roll the same ball fast and they scatter everywhere. The faster a thing goes, the more motion energy it carries, so it gives a bigger push when it hits something. Faster always means more energy to do work.
Heavier Means More Energy Too
Weight also changes how much motion energy a thing carries. Picture a light ping-pong ball and a heavy bowling ball rolling at the very same speed. The heavy bowling ball carries much more motion energy. It can knock the pins down far harder than the light ball can. So two things give a moving object more energy: going faster and being heavier. Either one means a bigger push.
Worked examples
You roll the same ball at pins slowly, then fast. Which roll pushes harder?
- A faster thing carries more motion energy than a slower thing.
- More motion energy gives a bigger push when it hits the pins.
- The fast roll has more motion energy than the slow roll.
Answer: The fast roll pushes the pins harder because it carries more motion energy.
A heavy ball and a light ball roll at the same speed. Which carries more energy?
- Both balls move at the same speed, so speed is equal.
- Weight also adds motion energy, and the heavy ball weighs more.
- More weight at the same speed means more motion energy.
Answer: The heavy ball carries more motion energy because it weighs more.
Activity
Predict which moving object will give the toy pins the biggest push.
Practice
Explain why a fast bike is harder to stop than a slow one.
Tell which gives a bigger push, a heavy cart or a light one moving alike.
Common mistakes to avoid
- a still heavy thing pushes hardMotion energy only comes from moving, so a still thing pushes nothing.
- speed does not change a ball's pushA faster ball carries more motion energy and pushes things much harder.
Check your understanding
You roll the same ball at the pins twice. Which roll gives the pins a bigger push?
Two balls roll at the very same speed: a heavy bowling ball and a light beach ball. Which carries more energy to push things?
Which sentence is true about a parked, still toy car?
Recap
Any moving thing carries motion energy that can push other things. Going faster gives more motion energy, and being heavier gives more too. A still object has no motion energy, so it cannot push anything until it moves.
Reflect
What moving thing did you see push something today, and why?