Idea 1of 5Builds onHow fast the speed changes
Two motions at once
Which ball lands first?
Today you'll discover
- two balls let go at the same instant
- why they stay level with each other
- the word for a thrown thing
Think firstOne ball dropped, one fired sideways. Same instant.
Same height, same instant. One dropped, one fired sideways. Which lands first?
Predict first, then press Next. Watch whether the two balls stay level.
A block with two balls at its top corner. After a prediction, the frames advance: the dropped ball falls straight down and the fired ball moves out as it falls, a dashed line joining them at the same height each time, until both reach the ground at the same moment. Then the fired ball's curved path is drawn. The last step fires the ball faster and asks again.
See the whole ideathe big idea and the key word, in one place
The big idea
A projectile: steady across, falling down, sharing one clock.
Easy to get wrongA faster throw does not fall more slowly. Gravity pulls every ball down the same way, whatever it does sideways.
Key word
- projectile
- an object moving under gravity alone after being thrown or launched: steady motion across, free fall down
About this modelAir is ignored: the ball is drawn as it would move in a vacuum.
Air is ignored: the ball is drawn as it would move in a vacuum.
Ready to use it?
- Say which of two launched balls lands first, and why.