Science (English Medium) कक्षा ११ - CBSE Question Bank Solutions for Physics

Explain why friction is necessary to make the disc in Figure roll in the direction indicated

(a) Give the direction of frictional force at B, and the sense of frictional torque, before perfect rolling begins.

(b) What is the force of friction after perfect rolling begins?

Read the following statements below carefully and state, with reasons, if it is true or false.

The stretching of a coil is determined by its shear modulus.

The edge of an aluminium cube is 10 cm long. One face of the cube is firmly fixed to a vertical wall. A mass of 100 kg is then attached to the opposite face of the cube. The shear modulus of aluminium is 25 GPa. What is the vertical deflection of this face?

Fill in the blanks using the word(s) from the list appended with each statement

For the model of a plane in a wind tunnel, turbulence occurs at a ... speed for turbulence for an actual plane (greater / smaller)

Explain why To keep a piece of paper horizontal, you should blow over, not under, it

Explain why A spinning cricket ball in air does not follow a parabolic trajectory

Can Bernoulli’s equation be used to describe the flow of water through a rapid in a river? Explain.

In a test experiment on a model aeroplane in a wind tunnel, the flow speeds on the upper and lower surfaces of the wing are 70 m s^–1and 63 m s^–1 respectively. What is the lift on the wing if its area is 2.5 m²? Take the density of air to be 1.3 kg m^–3.

Figures (a) and (b) refer to the steady flow of a (non-viscous) liquid. Which of the two figures is incorrect? Why?

The cylindrical tube of a spray pump has a cross-section of 8.0 cm² one end of which has 40 fine holes each of diameter 1.0 mm. If the liquid flow inside the tube is 1.5 m min^–1, what is the speed of ejection of the liquid through the holes?

In deriving Bernoulli’s equation, we equated the work done on the fluid in the tube to its change in the potential and kinetic energy. (a) What is the largest average velocity of blood flow in an artery of diameter 2 × 10^–3 m if the flow must remain laminar? (b) Do the dissipative forces become more important as the fluid velocity increases? Discuss qualitatively.

A copper block of mass 2.5 kg is heated in a furnace to a temperature of 500 °C and then placed on a large ice block. What is the maximum amount of ice that can melt? (Specific heat of copper = 0.39 J g^–1 K^–1; heat of fusion of water = 335 J g^–1).

Answer the following question based on the P-T phase diagram of carbon dioxide:

Is CO₂ solid, liquid or gas at

1. –70 °C under 1 atm,
2. –60 °C under 10 atm,
3. 15 °C under 56 atm?

Answer the following questions based on the P–T phase diagram of CO₂:

CO₂ at 1 atm pressure and temperature – 60 °C is compressed isothermally. Does it go through a liquid phase?

Answer the following questions based on the P–T phase diagram of CO₂:

What happens when CO₂ at 4 atm pressure is cooled from room temperature at constant pressure?

Answer the following questions based on the P–T phase diagram of CO₂:

Describe qualitatively the changes in a given mass of solid CO₂ at 10 atm pressure and temperature –65 °C as it is heated up to room temperature at constant pressure.

Answer the following questions based on the P–T phase diagram of CO₂:

Describe qualitatively the changes in a given mass of solid CO₂ at 10 atm pressure and temperature –65 °C as it is heated up to room temperature at constant pressure.

Answer the following questions based on the P–T phase diagram of CO₂:

CO₂ is heated to a temperature 70 °C and compressed isothermally. What changes in its properties do you expect to observe?

A ‘thermacole’ icebox is a cheap and efficient method for storing small quantities of cooked food in summer in particular. A cubical icebox of side 30 cm has a thickness of 5.0 cm. If 4.0 kg of ice is put in the box, estimate the amount of ice remaining after 6 h. The outside temperature is 45 °C, and coefficient of thermal conductivity of thermacole is 0.01 J s^–1 m^–1 K^–1. [Heat of fusion of water = 335 × 10³ J kg^–1]

A brass boiler has a base area of 0.15 m² and thickness 1.0 cm. It boils water at the rate of 6.0 kg/min when placed on a gas stove. Estimate the temperature of the part of the flame in contact with the boiler. The thermal conductivity of brass = 109 J s ^–1 m^–1 K^–1; Heat of vaporisation of water = 2256 × 10³ J kg^–1.