Materials : Metals and Non-Metals — Science STD 8 — Question

Name the chemicals which are used in refrigerators, air conditioners and damage ozone layer when released in air.

The rear wheels of a tractor are very wide. Explain with reason.

Imagine that an object is falling through a long straight glass tube held vertical, air has been removed completely from the tube. The object does not touch the walls of the tube. Will the object experience any force of friction?

Name the device used to measure atmospheric pressure.

An archer stretches her bow while taking aim at the target. She then releases the arrow, which begins to move towards the target. Based on this information, fill up the gaps in the following statements using the following terms: muscular, contact, non-contact, gravity, friction, shape, attraction
(a) To stretch the bow, the archer applies a force that causes a change in its ____________ .
(b) The force applied by the archer to stretch the bow is an example of ____________ force.
(c) The type of responsible for a change in the state of motion of the arrow is an example of a ____________ force.
(d) While the arrow moves towards its target, the forces acting on it are due to ____________ and that due to ____________ of air.

Explain, why the virtual image cannot be taken on screen.

How might the loss of forest cover and changes in rainfall patterns lead elephants to enter human farms and villages?

Name all the major pollutants of air.

Explain why the surface of mortar and pestle (silbatta) used for grinding is etched again after prolonged use?