FAQ About Science !

1: How do Frost and Snow are formed?

Frost forms when damp air comes into contact with cold ground. Snow forms when the ice crystals of a cloud cannot melt while they are falling.

2: Rail road tracks must make gradual curves only to prevent trains from derailment at high speeds. Explain .

The sharper the curve, the more centripetal force the train needs to accelerate around the centre.

3: Why are telescopes put on mountain peaks?

Optical telescopes need a clear view of the night sky. Therefore telescopes are sited in observatories on high mountain peaks, where the air is thinner and clearer. Stars are best viewed from space.

4: The laces of a shoe resemble a multiple pulley. If there are ten lace segments connecting one side of a shoe to the other, how much tension would you have to exert on the laces to pull the two sides together with a force of 400N?

400N divided by 10 equal segments equals 40N.

5: What do you mean by saying the olive oil is viscous?

The attraction between molecules of olive oil mean that they are less free-moving than those in water, giving the oil higher viscosity and thus making it flow more slowly.

6: When you breathe out, air flows rapidly out of your mouth. Where is that air's kinetic energy come from?

From pressure potential energy provided by your lungs.

7: How does a pigeon taken a long way away come back home?

Pigeons have cells in their brains which contain tiny particles of magnetite which are attracted by the Earth's magnetic field.

8: Why does shaking your wet hand remove the water?

As your hand accelerates the water is left behind.

9: What happens physiologically when you swim?

The heart beats faster, the lungs breathe more quickly and the muscles work harder.

10: Why does an ice cube usually crack when you take it directly from the freezer and drop it into a glass of water?

Its non-uniform thermal expansion produces huge stresses.

11: Whenever four soap bubble walls coming together one of them usually breaks. Explain

It is because three walls coming together are more stable or steady than four.

12: Why do you have time zones?

Time is not the same all around the Earth because the Earth turns once on its axis in just under 24 hours.

13: How do certain small insects emit light?

Glow-worms and fireflies make their own light from chemical reactions inside their bodies.

14. Why the flash-light produces incoherent light?

Because the photons of incoherent light are independent, their individual electric fields do not fluctuate together.

15: How can a tornedo pick up large objects?

The wind in tornedo exerts tremendous drag forces on objects.

16: Moth-balls are made from a white solid known as naphthalene that has strong odour. If you leave a moth-ball out why does it slowly disappear?

The napththalene sublimes and the moth-ball becomes gaseous.

17: Why is it important to keep foods and drugs out of direct sunlight, even when they are not in danger of over-heating.

Photons in sunlight can cause chemical damage.

18: What causes the javelin thrower to point downward at the end of the flight?

The javelin is designed with its centre of mass ahead of its physical centre so that it will land point down at the end of trajectory.

19: If you overload extension cord so that it is carrying too much electric current, why does it become hot?

Overload cord has a large voltage drop and consumes considerable electric power. It produces thermal energy.

20: How do hail-stones form?

If rain-drops pass through a layer of very cold air on their way down, their outer surface freezes. They then change into little translucent balls. A hail-stone generally measures 0.5 centimeters and above.

21: Why wet hair is much limper than dry hair?

Because water plasticizes hair temporarily softening it.

22: Why should the archer aim above the bull's-eye?

The bullet or arrow will fall in projectile flight so it must be compensated for its loss of height.

23: How does a bulb glow?

A light bulb can turn electricity into light because it contains a very thin filament. The electricity finds it very hard to flow through the filament, so it turns into heat which makes the filament glow white-hot.

24: Why do you see a rainbow while standing with your back to sunshine and looking towards a shower of rain?

Each of rain-drop directs some sunlight to your eye by splitting the light into colours.

25: Why do you add ethylene glycol to the water in radiator of the car engine during cold weather?

Ethylene glycol prevents the water from freezing. It is a substance that lowers the freezing point of water.

26: When a photocell operates from sunlight it is a form of heat engine. Explain .

A photocell converts some heat (thermal radiation) into ordered energy (electric energy) as it flows from the hot sun to the coolearth.

27: If an astronaut in an orbiting spaceship lights a candle why does the flame look peculiar?

There would be no convection to draw the flame upward.

28: Why aero-planes must have wings?

To position its centre of aerodynamic pressure properly behind its centre of mass the aero- plane must have two balanced wings.

29: Your body is converting chemical potential energy from food into thermal energy. If heat flows out of your body what happens to body temperature?

Your body temperature decreases.

30: Why laser lights are used in spectacular light shows?

The beam of laser light can travel through distances without spreading or fading.

31: A coin tips over when you stand it on edge, but it stays up on its edge when the coin is spinning. Explain?

The conserved quantity helps to keep it up-angular momentum.

32: What for racing-bicycles are made of very light materials?

To cut inertia to a minimum.

33: You can pop popcorn directly in a microwave oven simply by putting the corn in a paper bag. Why?

Microwaves heat the water in the kernels directly.

34: Can we hear every sound?

No. Some sounds are too high-pitched (ultrasonic) or too low-pitched (infrasonic) for our ears. But some animals such as dogs and horses can hear them.

35: Why a pie dish tips over after it is thrown?

A pie dish obtains lift from the air but the overall aerodynamic force on the dish is located ahead of the dish's centre of mass. As a result air exerts a torque on the dish about its centre of mass and changes dish's axis of rotation.