Some Natural Phenomena — Science STD 8 — Question

Name a non-metal which is very hard.

A Voltaic cell, also known as a Galvanic cell, contains two metal plates made of different materials and a liquid called an electrolyte, placed in a glass or plastic container. The plates, called electrodes, are partly dipped in the electrolyte, which is usually a weak acid or a salt solution. A chemical reaction between the plates and the electrolyte produces electricity.
(a) In what way is the Voltaic cell different from the dry cell?
(b) Who discovered the Voltaic or the Galvanic cell? What was the difference of opinion between the two scientists about the electricity generation by the cell, and how was it resolved?

Is any force being applied to an object in a non-uniform motion?

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?

It is advised to include physical exercise in daily routine. Give reason.

Name the agency responsible for development of space science programmes in India.

Which of the following are secondary sexual characteristics? Ovaries, Moustache, Penis, Broad hips, Vagina, Beard, Breast, Adam’s Apple, Wide shoulders, uterus, Testes, Deeper voice.

Which of the following are non-contact forces ? Magnetic force, Frictional force, Gravitational force, Muscular force, Electrostatic force.