English Medium Class 9 - CBSE Question Bank Solutions for Science

Arrange these statements in the correct sequence of preparation of green manure.

(a) Green plants are decomposed in soil.

(b) Green plants are cultivated for preparing manure or crop plant parts are used.

(c) Plants are ploughed and mixed into the soil.

(d) After decomposition it becomes green manure.

When will you say a body is at uniform acceleration?

Name the three sub-atomic particles of an atom.

Helium atom has an atomic mass of 4 u and two protons in its nucleus. How many neutrons does it have?

Compare the properties of electrons, protons and neutrons.

A neutron is formed by an electron and a proton combining together. Therefore, it is neutral.

The mass of an electron is about `1/2000` times that of proton.

A farmer moves along the boundary of a square field of side 10 m in 40 s. What will be the magnitude of displacement of the farmer at the end of 2 minutes 20 seconds?

Which of the following is true for displacement?

1. It cannot be zero.
2. Its magnitude is greater than the distance travelled by the object.

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?

An object experiences a net zero external unbalanced force. Is it possible for the object to be travelling with a non-zero velocity? If yes, state the conditions that must be placed on the magnitude and direction of the velocity. If no, provide a reason.

Why is it difficult to hold a school bag having a strap made of a thin and strong string?

In which of the three media, air, water or iron, does sound travel the fastest at a particular temperature?

Flash and thunder are produced simultaneously. But thunder is heard a few seconds after the flash is seen, why?

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.

A sound wave travels at a speed of 339 m s⁻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 m s⁻² and speed of sound = 340 m s⁻¹.

Is displacement a scalar quantity ?

State whether distance is a scalar or a vector quantity.

Under what conditions can a body travel a certain distance and yet its resultant displacement be zero ?