English Medium Class 9 - CBSE Question Bank Solutions

What is the cause of buoyant force ?

When a boat is partially immersed in water, it displaces 600 kg of water. How much is the buoyant force acting on the boat in newtons ? (g = 10 m s^-2)

When does an object float or sink when placed on the surface of a liquid ?

If a fresh egg is put into a beaker filled with water, it sinks. On dissolving a lot of salt in the water, the egg begins to rise and then floats. Why ?

A boy get into a floating boat.

What happens to the buoyant force on the boat ?

Four cars A, B, C and D are moving on a levelled, straight road. Their distance-time graphs are shown in the given figure. Which of the following is the correct statement regarding the motion of these cars?

A student draws a distance-time graph for a moving scooter and finds that a section of the graph is horizontal line parallel to the time axis. Which of the following conclusion is correct about this section of the graph?

'When a hanging carpet is beaten with a stick, the dust particles start coming out of it'. This phenomenon can be best explained by making use of :

An object of mass 2 kg is sliding with a constant velocity of 4 m/s on a frictionless horizontal table. The force required to keep this object moving with the same velocity is :

State whether the following statement is true or false :

Milk is a pure substance.

Name one metal and one non-metal which exist as liquids at room temperature.

In a cluster of hutments, many people are suffering from malaria. Mention the unhygienic conditions that must be prevailing in that locality. How does a doctor confirm malaria?

Name any three diseases of human beings caused by bacteria and three diseases caused by virus.

Explain how does the body react after the entry of microbe in the body.

Distinguish between symptoms and signs of a disease.

Write down the causal organisms of the following diseases :

Tuberculosis, Kala-azar, Malaria, Measles, Athlete's foot, Cholera.

Write short notes on

(a) AIDS;

(b) Malaria.

Describe certain bacterial diseases of human beings.

Give an account of some important viral diseases of human beings.

Write short notes on

(a) Tuberculosis;

(b) Polio.