English Medium Class 9 - CBSE Question Bank Solutions for Science

In the case of negative work, the angle between the force and displacement is

A girl is carrying a school bag of 3 kg mass on her back and moves 200 m on a levelled road. The work done against the gravitational force will be (g = 10 m s^–2)

An automobile engine propels a 1000 kg car (A) along a levelled road at a speed of 36 km h^–1. Find the power if the opposing frictional force is 100 N. Now, suppose after travelling a distance of 200 m, this car collides with another stationary car (B) of the same mass and comes to rest. Let its engine also stop at the same time. Now the car (B) starts moving on the same level road without getting its engine started. Find the speed of the car (B) just after the collision.

A girl with having a mass of 35 kg sits on a trolley of mass 5 kg. The trolley is given an initial velocity of 4 m s^–1 by applying a force. The trolley comes to rest after traversing a distance of 16 m. (a) How much work is done on the trolley? (b) How much work is done by the girl?

The atmosphere of the earth is heated by radiations which are mainly

The two forms of oxygen found in the atmosphere are

Choose the correct sequences

An increase in carbon dioxide content in the atmosphere would not cause

Which one is not a source of carbohydrates?

The crops which are grown in the rainy season are called ______ crops.

Why is organic matter important for crop production?

If there is low rainfall in a village throughout the year, what measures will you suggest to the farmers for better cropping?

Cultivation practices and crop yield are related to environmental conditions. Explain.

Differentiate between the following

Mixed cropping and Intercropping

The mass per unit volume of a substance is called density.

(density = mass/volume).

Arrange the following in order of increasing density-

air, exhaust from chimneys, honey, water, chalk, cotton and iron.

Tabulate the differences in the characteristics of states of matter.

Comment upon the following:

rigidity, compressibility, fluidity, filling a gas container, shape, kinetic energy and density.

Give reasons:

A gas fills completely the vessel in which it is kept.

Give reasons:

A gas exerts pressure on the walls of the container.

Give reasons:

We can easily move our hand in air, but to do the same through a solid block of wood, we need a karate expert.