List of top Science Questions asked in CBSE Class IX

Look at the activities listed below. Reason out whether or not work is done in the light of your understanding of the term ‘work’.
• Suma is swimming in a pond.
• A donkey is carrying a load on its back.
• A wind-mill is lifting water from a well.
• A green plant is carrying out photosynthesis.
• An engine is pulling a train.
• Food grains are getting dried in the sun.
• A sailboat is moving due to wind energy.

What is the importance of universal law of gravitation?

Two children are at opposite ends of an aluminium rod. One strikes the end of the rod with a stone. Find the ratio of times taken by the sound wave in air and in aluminium to reach the second child.

An object of mass \(40\) \(kg\) is raised to a height of \(5\) \(m\) above the ground. What is its potential energy? If the object is allowed to fall, find its kinetic energy when it is half-way down.

An object of mass, m is moving with a constant velocity, v. How much work should be done on the object in order to bring the object to rest?

Convert the following temperatures to the Celsius scale.
(a) 293 K
(b) 470 K

Arrange the following substances in increasing order of forces of attraction between the particles— water, sugar, oxygen.

An athlete completes one round of a circular track of diameter  \(200 \;m\) in \(40 \;s\). What will be the distance covered and the displacement at the end of \(2\) minutes \(20\) \(s\)?

Calculate the work required to be done to stop a car of 1500 kg moving at a velocity of 60 km/h?

Abdul, while driving to school, computes the average speed for his trip to be \(20\) \(km\, h^{–1}\). On his return trip along the same route, there is less traffic and the average speed is \(30\) \(km \,h^{–1}\). What is the average speed for Abdul’s trip?

An electric heater is rated 1500 W. How much energy does it use in 10 hours?

In each of the following a force, F is acting on an object of mass, m. The direction of displacement is from west to east shown by the longer arrow. Observe the diagrams carefully and state whether the work done by the force is negative, positive or zero.

If the moon attracts the earth, why does the earth not move towards the moon?

Give two practical applications of reflection of sound waves.

A freely falling object eventually stops on reaching the ground. What happenes to its kinetic energy?

Identify the solutions among the following mixtures.

How do you differentiate between capture fishing, mariculture and aquaculture?

Soni says that the acceleration in an object could be zero even when several forces are acting on it. Do you agree with her? Why?

Explain how defects in a metal block can be detected using ultrasound.

How is ultrasound used for cleaning?

What is loudness of sound? What factors does it depend on?

What is reverberation? How can it be reduced?

A sound wave travels at a speed of 339 ms^–1. If its wavelength is 1.5 cm, what is the frequency of the wave? Will it be audible?

A stone is dropped from the top of a tower 500 m high into a pond of water at the base of the tower. When is the splash heard at the top? 
Given, g = 10 ms^–2 and speed of sound = 340 ms^–1.