CBSE NCERT Solutions for Class 8 Science Chapter 11

The NCERT solutions given here includes all the chapter-wise & exercise-wise solutions to class 8 science NCERT questions. The solutions are easy to understand and are given in simple words.

CBSE NCERT Solutions for Class 8 Science Chapter 11:


What is a cyclone? What is the reason for the formation of cyclones?


Cyclone refers to any spinning storm that rotates around a low-pressure center. The
low-pressure center is also referred to as the 'eye' of the storm, which is well known for being eerily calm compared with the areas under the spinning 'arms' of the storm. Cyclones are basically created by the differences in air pressure. A cyclone is formed when a system of winds moving in circular motion closes in toward an area of the sea with low atmospheric pressure.


Explain the following:
a. Why can't we hammer a nail by its head on the wood?
b. A sharp knife cuts better than a blunt knife. Why?


a. The head of the nail has a larger area than the tip so the pressure is reduced in case of hammering the head instead of the tail.
b. A sharp knife has a lesser surface area than blunt one, so, a sharp knife applies a greater pressure when used for cutting.


Explain the following:
A. Why does a helium balloon burst when it rises too high up?
B. Why do we feel nauseated when we go deep into the water?


A. Pressure decreases as we go up in the atmosphere so when the helium balloon
rises up the pressure inside the balloon becomes more than the pressure outside and so the balloon first expand and then finally bursts.
B. As we go deep into the water the pressure increases. So now there is higher pressure outside and less pressure inside the body. So our lungs feel crushed and we feel nauseated.


Why is it difficult to pull out a rubber sucker stuck to surface like glass?


When you press the rubber sucker on a surface, most of the air between it and the surface escapes out. The sucker sticks to the surface because the pressure of atmosphere acts on it. To pull the sucker off the surface, the applied force should be large enough to overcome the atmospheric pressure. And that force is quite large. And that’s why it’s hard to pull off the rubber sucker from a surface.