English Medium इयत्ता ९ - CBSE Question Bank Solutions for Science

What do you mean by the term free fall ?

During a free fall, will heavier objects accelerate more than lighter ones ?

Give reason for the following :
The force of gravitation between two cricket balls is extremely small but that between a cricket ball and the earth is extremely large.

Explain why, if a stone held in our hand is released, it falls towards the earth.

What is the force of gravity on a body of mass 150 kg lying on the surface of the earth? (Mass of earth = 6 x 10²⁴ kg; Radius of earth = 6.4 x 10⁶ m; G = 6.7 x 10^-11 Nm²/kg²)

What do you understand by the term 'acceleration due to gravity of earth' ?

What is the usual value of the acceleration due to gravity of earth ?

The values of g at six distances A, B, C, D, E and F from the surface of the earth are found to be 3.08 m/s², 9.23 m/s², 0.57 m/s², 7.34 m/s², 0.30 m/s² and 1.49 m/s², respectively.
(a) Arrange these values of g according to the increasing distances from the surface of the earth (keeping the value of g nearest to the surface of the earth first)
(b) If the value of distance F be 10000 km from the surface of the earth, state whether this distance is deep . inside the earth or high up in the sky. Give reason for your answer.

Why does a sharp knife cut objects more effectively than a blunt knife ?

Explain why, a wide steel belt is provided over the wheels of an army tank.

Explain why, the tip of a sewing needle is sharp.

Name the force which wears away two surfaces as they move over one another.

Name the force which pulled the apple off Isaac Newton’s tree.

Name the force which stops you falling through the floor.

A pressure of 10 Pa acts on an area of 3.0 m². What is the force acting on the area ? What force will be exerted by the application of same pressure if the area is made one-third ?

"A substance has a definite shape as well as a definite volume." Which physical state is represented by this statement?

Give one example of the diffusion of a solid in another solid.

Explain why, the diffusion of a solid in another solid is a very slow process.

State two characteristic properties of a solid.