Force and Laws of Motion — Science STD 9 — Question

A certain species X has 17 protons, 18 electrons and 20 neutrons.

1. What is such a particle called?
2. What is the mass number of X?
3. What is the atomic number of X?

A constant force acts on an object of 5kg for a period of 2s. It increases the velocity of an object from 3m/s to 7m/s. Find the magnitude of the applied force. Now, if the force was applied for a period of 5s, then what would be the final velocity of the object?

Give reasons for:
It is difficult to pull out the husk of a coconut tree.

Complete the following table.

Elements	Atomic number	Mass number	Protons	Electrons	neutrons	Electronic configuration	Valency
Chlorine	17	___	___	___	18	___	___
Silicon	___	28	___	14	___	___	___
Fluorine	___	___	9	___	10	___	___

Write any two applications of Archimedes' principle.

Comment on the following statements:

1. Evaporation produces cooling.
2. Rate of evaporation of an aqueous solution decreases with increase in humidity.
3. Sponge though compressible is a solid.