Is Matter Around Us Pure ? — Science STD 9 — Question

Describe how the gravitational force between two objects depends on the distance between them.

Complete the following table.

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

Name the scientist who studied the movement of pollen grains suspended in water through a microscope. What is this phenomenon known as?

A body of mass 5kg is moving with a velocity of 10m/s. A force is applied to it so that in 25 seconds, it attains a velocity of 35m/s. Calculate the value of the force applied.

If a sprinter runs a distance of 100 metres in 9.83 seconds, calculate his average speed in km/h.

How does the weight of an object vary with respect to mass and radius of the earth. In a hypothetical case, if the diameter of the earth becomes half of its present value and its mass becomes four times of its present value, then how would the weight of any object on the surface of the earth be affected?

A ball falls to the ground as shown below:

1. ♦ Potential energy = 80 J, Kinetic energy = 0
2. ♦ Kinetic energy = 48J
3. ♦ Potential energy = 0

1. What is the kinetic energy of ball when it hits the ground?
2. What is the potential energy of ball at B?
3. Which law you have made use of in answering this this question?