Solution to Activity 8.3 of NCERT Class 9 Science Chapter 8 Force and Laws of Motion

3. Complete Activity 8.3 (Page 91).

• Place a water-filled tumbler on a tray.

• Hold the tray and turn around as fast as you can.

• We observe that the water spills. Why?

Answer:

Aim: To observe what happens when you hold the tray and turn around fast and conclude based on that.

Materials Required: Water, tumbler, tray.

Procedure:

(i) Place the water-filled tumbler on the tray gently.

(ii) Now hold and tray and whirl around as fast as possible. Observe what happens.

Observations: The water spills out from the glass tumbler.

Hand holding a tumbler on a tray, which is being whirled around. — **Inertia of Rest:** When you turn around the water spills from the tumbler. Let us find out why.

Conclusions:

When the tray is whirled around, the water in the tumbler spills. This is because the lower portion of the tumbler is in motion along with the tray, but the upper portion tends to retain its state of rest due to inertia. Hence, the tumbler falls backwards.

“• Place a water-filled tumbler on a tray.

• Hold the tray and turn around as fast as you can.

• We observe that the water spills. Why?” – Solved.