Explanation

The force the earth attracts a body towards itself is called weight.

It is not constant but varies from place to place due to changes in the value of g

 Since it is a force, its SI unit is also Newton (N).

Explanation

Clear nights are cooler than cloudy nights because of radiation. Here's why:

• On a clear night, the Earth's surface rapidly loses heat by radiating it into space, a process known as radiative heat loss. This causes the temperature to drop.
• On a cloudy night, the clouds act as an insulating blanket, trapping heat and preventing it from escaping into space. This reduces radiative heat loss and keeps the temperature warmer.

Explanation

Surface tension acts like a stretched membrane on the water's surface, and the surface tension along the blade's edges is greater than the blade's weight.

The force of surface tension acts tangentially to the liquid surface on the circumference of the blade.

Explanation

A weather balloon is not fully inflated on the ground because the air inside the balloon would expand and may burst as it rises.

The atmosphere is less dense at higher altitudes, so the pressure inside the balloon becomes greater than the pressure outside.

This causes the balloon to expand until it reaches its elastic limit and bursts.

Weather balloons typically burst at altitudes of over 15 miles (24.1 kilometers).

If a balloon were fully inflated on the ground, the gas would need to be vented out and wasted as it expands. 

Explanation

• Tungsten is very resistant to corrosion and has the highest melting point (melting point = 3695 K) and the highest tensile strength of any element.
• Tungsten is used for making bulb filaments of incandescent lamps because it has the highest melting point and does not melt even while it is glowing for long hours.