for use with materialworlds Newton's cradle simulation
© materialworlds.com 2001
In the classic demonstration of Newton's cradle a ball hits one end of a line of stationary balls and out pops the ball at the other end of the line. The balls in between seem to stay stationary. In this experiment you'll watch in slow motion to see what really happens.
First watch the simulation at "normal" speed, then "slow" and sometimes "v. slow" to look in detail at what happens in the vital milliseconds between a ball hitting one end of the line of balls and a ball leaving the other end.
1. The diagrams below show the positions of the balls at a set of key moments - from before a ball hits from the right through to a ball leaving the left of the line.
Draw in the blue velocity arrows for the balls for each of these moments. Then add in the resultant forces (red triangle headed arrows).
Hint: Switch to "slow" mode and
rewind the
simulation. Before the first collision, switch to "v. slow" mode. 
Pause the
simulation each time a collision occurs (you'll hear a click and see the
collision forces).
2. Explain what forces the balls experience as they collide - and how these forces change the balls' motion.