WHY DO SHOES HAVE HEELS? DO THEY HELP IN WALKING?

The human foot is designed to walk on grassy or muddy surfaces not on hard concrete or marble. Walking barefoot on such hard artificial surfaces jolts our body and jars the spine. Heels on shoes provide cushioning to the body. The heel requires more cushioning than the rest of the foot because it bears the brunt of the impact with the ground.

In addition to cushioning the foot, the heel also ensures durability of the shoe. A shoe without a heel would soon wear out in the heel region. You can do it because your shoes cushion your feet from injury.

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WILL A PAPER IN A GLASS WATER REMAIN DRY?

What you will need

A wad of old newspaper, large plastic tub, glass tumbler, water.

What you do:

  • Fill the tub with water.
  • Scrunch up the newspaper and stuff it in the bottom of the glass tumbler. upside down to make sure that the paper does not slip out.
  • Holding the tumbler upside down, plunge it straight down to the bottom of the tub.
  • Pull out the glass from the water.
  • Do not tip the glass to the side at any time during the experiment.

What do you observe?

 When you take out the newspaper, you will find that it is absolutely dry!

Why does this happen?

 Air occupies space. When you submerge the tumbler, the air inside the glass cannot escape. It acts as a block, preventing the water from entering the glass. Hence the newspaper does not get wet.

Picture Credit : Google 

Does the water from a tap flow uniformly?

What you do:

  • Turn on the tap.
  • Watch the water flow.

What you see:

The stream of water is initially of the same size as the opening of the mouth of the tap but it decreases in size as it flows.

Why does this happen?

Surface tension tends to hold the water in a solid stream at the top but as it falls, its speed increases because of the pull of gravity.

When the flow of water is continuous, the amount of water passing through any point should be the same. The amount of flow is determined by the cross sectional area of the stream multiplied by the speed of flow of the water. As the speed of the water increases due to gravity. its size reduces.

Picture Credit : Google 

 

When you pour tea (water or any other liquid) from a vessel into a glass, you see bubbles on the surface of the tea inside the glass. Do these bubbles form every time you pour the tea?

What you need:

A glass and a vessel with tea What you do:

Hold the vessel high above the glass and pour the tea into it. What do you find? Bubbles form on the surface of the tea inside the glass. Next hold the vessel close to the glass and pour the tea into it.

What do you find?

Bubbles don't form on the surface of the tea inside the glass.

What's the reason?

Due to surface tension, the surface of a liquid behaves like a stretched membrane or skin'. When you pour tea into the glass while holding the vessel close to it the tea falling gently cannot penetrate the skin of the tea in the vessel. But when you pour it from a great height, it strikes the surface of the tea in the glass with great force. The skin breaks trapping air, which bubbles back to the surface.

Picture Credit : Google

Is the air cooler when you blow with your mouth open wide or with pursed lips?

What you do:

• Open your mouth wide and blow air into your palm. Observe.

• Then purse your lips and blow air into your palm. Observe.

What you find:

The air is warmer when you blow with your mouth wide open.

Why?

The temperature of the air coming out of the open mouth is more or less the same as that of the body, and hence it is warm. When you purse your lips, the air gets compressed and comes out in a thin stream but once, outside, it expands and cools. Another reason for the difference is that the fast moving stream of air draws in cool air from the surroundings.

Picture Credit : Google