Fig. 2
A. Experiment of normal collision between two carts which have the same mass.
1) Set a stick on one end of the large wooden dynamic cart and set an anchoring rod of force sensor to
the metallic dynamic cart. Note: Mass of each cart is 1 kg.
2) Tie the stick of wooden cart to the anchoring rod of metallic cart with a rubber band (see Fig. 2).
3) Place a stick in the middle between the two carts (see Fig. 2).
4) Move the carts apart around the same distance from where the stick is placed in the middle (the
recommended distance between them is less than 30cm).
5) If you release them at the same time, the two carts are going to collide in the middle, and then each
cart is going to move back to its original position.
B. Experiment of collision between two carts with different masses
1) Set a stick on one end of the large wooden dynamic cart and set an anchoring rod of force sensor to
the metallic dynamic cart. Note: Mass of each cart is 1 kg.
2) Place the other metallic dynamic cart on the wooden dynamic cart (see Fig. 2) to double its mass.
Therefore, the mass ratio of metallic cart and wooden cart unit (with a metallic cart on top) is 1 : 2.
3) Tie the stick of wooden cart to the anchoring rod of metallic cart with a rubber band (see Fig. 2).
4) Place a stick in the middle between two carts (see Fig. 2).
5) Move the carts apart around the same distance from where the stick is placed in the middle (the
recommended distance between them is less than 30cm).
6) If you release them at the same time, the two carts are going to collide in the middle, and then each
cart is going to move back to its original position even though their masses are different.
Additional information: because the metallic cart on top of the wooden cart can move freely without
almost any friction, its mass does not play any role in the collision due to the law of inertia. On the other
hand, if we would fix the metallic cart (for example placed it upside down) onto the wooden cart, its
mass does play a role in the collision and then the collision does not occur in the middle where the stick
is placed.
