Put a piece of chalk into water. The chalk will emit bubbles in all directions. Explain

Water from a sprinkler comes out with a constant velocity u in all the directions. What is the maximum area of the grassland that can be watered at any time?

Ten one-rupee coins are put on top of each other on a table. Each coin has a mass m. Give the magnitude and direction of (a) the force on the 7th coin (counted from the bottom) due to all the coins on its top,(b) the force on the 7th coin by the eighth coin, (c) the reaction of the 6th coin on the 7th coin.

Take a table - tennis ball and make three slits into it. put semicircular fins cut out of a metal sheet into these slits. Pivot the tennis ball on an axle through its centre with a straight metal wire fixed to a rigid support. Now connect a cycle dynamo to this. connect a bulb in series. Direct a jet of water or steam produced in a pressure cooker at the fins. What do you observe ?

The mass per unit volume of a substance is called density. (Density = mass/volume). Arrange the following in order of increasing density- air, exhaust from chimneys, honey, water, chalk,cotton and iron.

Bubbles of air coming out through water in glass vessel appears silvery to an observer standing by the sides Explain the reason.

Explain why Water on a clean glass surface tends to spread out while mercury on the same surface tends to form drops. (Put differently, water wets glass while mercury does not.)