Combustion and flame — Science STD 8 — Question

If a vacuum is created between two Magdeburg hemispheres joined together, they cannot be separated easily, What presses the hemispheres together?

Whenever we push a very heavy box kept on the ground, it does not move at all because frictional force balances the force that we apply. So, there is no net movement of this box. It acts in a direction opposite to the force we apply.

Can the process of rusting be called combustion? Give reason for your answer.

Which properties of chromium metal make it suitable for electroplating it on car bumpers, bath taps and bicycle handlebars, etc., made of iron?

What is muscular force ? Give one example of muscular force.

What happens to the tail of a comet when it moves far away from the Sun?

What is noise? Give two examples of sounds which are considered noise.

Which characteristics of Mars distinguishes it from other planets?

A gland W is located just below the stomach in the human body. The gland W secrets a hormone X. The deficiency of hormone X in the body causes a disease Y in which the blood sugar level of a person rises too much. The person having high blood sugar is called Z. What are W, X, Y and Z?

Explain how the position of Sirius Star can be located in the night sky with the help of Orion constellation.