Question

Newton's Cradle consists of an aligned row of identical elastic balls suspended by strings so they barely touch one another. When two balls are raised from one end and released, they strike the row and two balls pop out from the other end. If instead, one ball popped out with twice the speed of the two, this would violate ____.

Answer 1

When two balls are raised from one end and released, they strike the row and two balls pop out from the other end. If instead, one ball popped out with twice the speed of the two, this would violate law of conservation of energy.

Step-by-step explanation:

"According to law of conservation of energy, energy can neither be created nor destroyed it only changes it's states."

we can prove it as

the initial momentum = 2mv

if one ball popped out with 2v then the momentum would be conserved.

But the initial kinetic energy of these two balls are given as

`(1)/(2)mv^(2) +(1)/(2)mv^(2) = mv^(2)`

but if the speed of one ball is twice then that of other one then the kinetic energy won't remain conserved.

`K.E = (1)/(2)m(2v)^(2) = 2mv^(2)`

thus it violates the law of conservation of energy.