English Medium इयत्ता ९ - CBSE Question Bank Solutions for Science

What is the acceleration of free fall?

A ball is thrown vertically upwards with a velocity of 49 m/s. Calculate

1. the maximum height to which it rises.
2. the total time it takes to return to the surface of the earth.

A stone is released from the top of a tower of height 19.6 m. Calculate its final velocity just before touching the ground.

A stone is thrown vertically upward with an initial velocity of 40 m/s. Taking g = 10 m/s², find the maximum height reached by the stone. What is the net displacement and the total distance covered by the stone?

A stone is allowed to fall from the top of a tower 100 m high and at the same time another stone is projected vertically upwards from the ground with a velocity of 25 m/s. Calculate when and where the two stones will meet.

A ball thrown up vertically returns to the thrower after 6 s. Find

1. the velocity with which it was thrown up,
2. the maximum height it reaches, and
3. its position after 4 s.

A certain household has consumed 250 units of energy during a month. How much energy is this in joules?

Suppose you and your friend are on the moon. Will you be able to hear any sound produced by your friend?

Describe with the help of a diagram, how compressions and rarefactions are produced in air near a source of sound.

Cite an experiment to show that sound needs a material medium for its propagation.

List any three human activities that you think would lead to air pollution.

Why is the atmosphere essential for life?

Which force is responsible for the moon revolving round the earth ?

What is the acceleration produced in a freely falling body of mass 10 kg ? (Neglect air resistance)

When an object is dropped from a height, it accelerates and falls down. Name the force which accelerates the object.

What force is responsible for the earth revolving round the sun ?

State whether the following statement is true or false :
A falling stone also attracts the earth.

State whether the following statement is true or false :

The acceleration due to gravity acting on a freely falling body is directly proportional to the mass of the body.

Fill in the following blank with suitable word :

The acceleration due to gravity on the moon is about ………………of that on the earth.

Explain what is meant by the equation :
`g= Gxxm/r^2`
where the symbols have their usual meanings.