Assemble the Newton's Cradle

     The time for Newton's cradle to swing varies depending on the force applied. Under normal conditions, the swing time is about 15 seconds, affected by air resistance.

 The Change of Five Balls

 This is a series of elastic collisions.It also includes inelastic collisions and momentum. Since there are no other forces affecting the collision, the momentum of the L ball with mass M and velocity VL must be transferred to the R ball on the right, which is stationary. The R ball with mass M that is hit after the collision has the same momentum. The balls that are hit both have a velocity to the right, VR, and a tendency to move to the right, which is called momentum conservation.

 The energy before and after the collision must be consistent, and the vibration motion of the ball is ignored here.