Science (English Medium) Class 11 - CBSE Question Bank Solutions

Is the bulb of a thermometer made of diathermic or adiabatic wall?

One day in the morning, Ramesh filled up 1/3 bucket of hot water from geyser, to take bath. Remaining 2/3 was to be filled by cold water (at room temperature) to bring mixture to a comfortable temperature. Suddenly Ramesh had to attend to something which would take some times, say 5-10 minutes before he could take bath. Now he had two options: (i) fill the remaining bucket completely by cold water and then attend to the work, (ii) first attend to the work and fill the remaining bucket just before taking bath. Which option do you think would have kept water warmer? Explain.

Which of the processes described below are irreversible?

1. The increase in temprature of an iron rod by hammering it.
2. A gas in a small cantainer at a temprature T₁ is brought in contact with a big reservoir at a higher temprature T₂ which increases the temprature of the gas.
3. A quasi-static isothermal expansion of an ideal gas in cylinder fitted with a frictionless piston.
4. An ideal gas is enclosed in a piston cylinder arrangement with adiabatic walls. A weight W is added to the piston, resulting in compression of gas.

Answer carefully, with reason:

Is the total linear momentum conserved during the short time of an inelastic collision of two balls ?

Action and reaction

(a) act on two different objects
(b) have equal magnitude
(c) have opposite directions
(d) have resultant zero.

For most of the surfaces used in daily life, the friction coefficient is less than 1. Is it always necessary that the friction coefficient is less than 1?

What is the average friction force when a person has a usual 1 km walk?

Why is it difficult to walk on solid ice?

Spring fitted doors close by themselves when released. You want to keep the door open for a long time, say for an hour. If you put a half kg stone in front of the open door, it does not help. The stone slides with the door and the door gets closed. However, if you sandwitch a 20 g piece of wood in the small gap between the door and the floor, the door stays open. Explain why a much lighter piece of wood is able to keep the door open while the heavy stone fails.

A classroom demonstration of Newton's first law is as follows : A glass is covered with a plastic card and a coin is placed on the card. The card is given a quick strike and the coin falls in the glass. (a) Should the friction coefficient between the card and the coin be small or large? (b) Should the coin be light or heavy? (c) Why does the experiment fail if the card is gently pushed?

Why do tyres have a better grip of the road while going on a level road than while going on an incline?

You are standing with your bag in your hands, on the ice in the middle of a pond. The ice is so slippery that it can offer no friction. How can you come out of the ice?

When two surfaces are polished, the friction coefficient between them decreases. But the friction coefficient increases and becomes very large if the surfaces are made highly smooth. Explain.

While walking on ice, one should take small steps to avoid slipping. This is because smaller steps ensure.

Consider the situation shown in figure. The wall smooth but the surface of A and B in contact are rough. The friction on B due to A in equilibrium

Suppose all the surface in the previous problem are rough. The direction of friction of B due to A

A spring-mass system oscillates with a frequency v. If it is taken in an elevator slowly accelerating upward, the frequency will