Activity 9.2 Class 9 Science Force and Laws of Motion
Activity 9.2 asks us to hit the card fast and see what happens to the coin.
The coin falls inside the glass.
This activity is similar to activity 9.1 also. There we struck the pile of coins using the striker.
Here the coin is at the rest also wants to remain at the rest: Newton's first law of motion. When we hit the card fast, the energy of the card does not transfer to the coin. As a result, the coin does not move and falls inside the glass due to gravity.
We strike fastly, else the frictional force between the coin and the paper will become high. This will result in the movement of either both or none, depending on the amount of the force.
Activity 9.1 Class 9 Science Force and Laws of Motion
Ref: Class 9 Science chapter 9.