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  • Check out how high these different balls

  • bounce-- the basketball, the super bouncy ball, and the golf

  • ball.

  • Now, I'm going to try the golf ball on top

  • of the bouncy ball on top of the basketball,

  • and then I'm going to explain how

  • it's related to a supernova.

  • Did you see that?

  • Probably not, so here it is again.

  • The golf ball bounced to 28 feet.

  • We dropped it from about 3 and 1/2 feet, so it went up 800%

  • of its dropped height.

  • In fact, if you consider that by itself-- the golf ball bounces

  • about 70% of it's dropped height--

  • it went as high as if it had fallen from 40 feet up.

  • That is awesome.

  • So how can we get the golf ball to bounce up

  • with that much energy?

  • Let's simplify it to these two balls.

  • When you drop them individually, each ball

  • starts out with some potential energy

  • from the height of the drop.

  • As the balls hit the ground, some energy

  • goes into heating up the ground, and some

  • goes into heating the ball.

  • Because that energy left the ball system,

  • you can't get back up to the same height.

  • But when you combine them, the tennis ball

  • goes higher than its dropped height, way higher.

  • Where does it get the extra energy?

  • As the basketball bounces, it compresses, storing

  • elastic potential energy.

  • As it releases, it springboards the tennis ball upward

  • just at the right moment.

  • This is like the double bounce on a trampoline

  • when you jump right before someone else.

  • You prepare the elastic of the trampoline

  • by stretching it and storing energy, which can then

  • bounce the jumper even higher.

  • In the same way, the basketball stores energy

  • in its compression and is able to push the tennis ball,

  • but just like the double bounce preparer,

  • the basketball can't go as high.

  • You can see that here.

  • It bounces even less when three balls are dropped together.

  • Also during that transfer of energy,

  • some momentum transfers from the basketball to the tennis ball,

  • and since the basketball starts with way

  • more momentum because of its larger mass, the tennis ball's

  • velocity increases by a lot.

  • And it flies up, up, and away.

  • Now, back to the triple super ball bounce.

  • Now, do you get the energy from the basketball's bounce being

  • transferred into the bounce of the super bouncy

  • ball, which is then transferred to the golf ball's bounce.

  • You put the same amount of energy or momentum

  • from two more massive objects into a smaller object,

  • and it will go much faster, epic,

  • just like the explosions of a supernova, which

  • may seem unrelated.

  • But what we just did is analogous to the process

  • that occurs during the explosion of a supernova.

  • Just like our more massive basketball transfers momentum

  • to the smaller balls, energy from the dense core

  • of the supernova is transferred in a shockwave that

  • moves through the star to the less dense layers

  • and accelerates them outward at a super high velocity.

  • More massive or denser layers in the core of the supernova

  • begin to collapse when fusion stops there.

  • The collapse is halted when the neutrons in the core

  • actually touch, sort of.

  • This causes the implosion to rebound and bounce outward.

  • You end up with a dense core left behind

  • and these wild outer shells of star exploding outward, pretty

  • cool.

  • And, of course, if you try this at home, which you should,

  • you have to make sure the balls are perfectly vertically

  • aligned because any off centeredness gets amplified

  • by the two points of contact, which

  • is why we sadly couldn't get the quadruple tower of balls

  • to work.

  • But if you put a little ring of hot glue or something

  • similar on the balls, it helps to balance them.

  • Happy physicsing.

  • [MUSIC PLAYING]

Check out how high these different balls

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B1 US ball bounce golf ball energy tennis ball golf

Stacked Ball Drop

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    Samuel posted on 2018/07/21
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