Physics is considered as one of the most difficult subjects in 11th standard. Most students fear the subject and fail to score well in the exam. But if students have a strong base of the topics and understand the concepts properly it can be very easy for them to excel in this subject. The important questions for physics class 11 are given here so that students can prepare for their exam more efficiently.

The Central Board of Secondary Education is one of the oldest and most preferred boards in India. CBSE conducts board examination for different classes along with class 10 and 12 mostly in the month of March every year. The board aims to provide a healthy education to all its students so that they can develop both mentally and physically. The CBSE questions are prepared by subject experts according to the latest CBSE syllabus.

The 3 marks questions in CBSE physics class 11 is the easiest and the most scoring section in the exam. With little practice, students can ace in this section which can increase their overall marks in the exam. The important 3 marks question for class 11 physics is given below to help students understand the concepts and prepare for their exam more effectively.

*The Important 3 marks Question for Physics Class 11th is given below. *

**Question 1- **Explain the concept of moment of inertia.

**Question 2- **State the law of conservation of energy and verify it in the case of freely falling object. Calculate the total energy of the body mass 5 kg which is freely falling from a height of 100m, at the highest point and at middle and at the lowest point.

**Question 3- **Explain the procedure to determine the coefficient of apparent expansion of a liquid using specific gravity bottle with relevant theory.

**Question 4-** A ring disc and a sphere, all of the same radius and mass roll down an inclined plane from the same height h. Which of the three reaches the bottom (i) earliest (ii) latest?

**Question 5- **A lorry and a car with the same kinetic energy are brought to rest by the application of brakes which provides equal retarding forces. Which of them will come to rest in a shorter distance.

**Question 6- **A bullet of mass m is fired from a gun of mass M. If the muzzle speed of the bullet is V, then what is the recoiling speed of the gun?

**Question 7- **State parallel axis theorem.

**Question 8- **Calculate the moment of inertia about the diameter if that of an axis perpendicular to the plane of a disc and passing through its centre given by \(\frac{1}{2}MR_{2}\).

**Question 9- **The amplitude of a simple harmonic oscillator is doubled. How does this effect:

(i) the maximum velocity

(ii) the total energy

(iii) period of oscillator

**Question 10- **Derive the expression for momentum conservation.

**Question 11-** What are nodes and antinodes? Do they coincide with pressure nodes and antinodes? In terms of X, what is the separation of a node from the nearest antinode? What is the phase difference between points separated by \(\frac{X}{10}\) in stationary waves?

**Question 12- **Suppose that centre of mass of a system of two particles lies on the straight line joining them.

**Question 13- **What is binding energy of a satellite?

**Question 14- **Figure(a) shows a spring of force constant K clamped rigidly at one end and a mass m attached to its free end. A force applied at the free end stretches the spring.

Figure (b) shows the same spring with both ends free and attached to mass m at either end. Each end of the spring in figure (b) is stretched by the same force F.

(i) What is the maximum extension for the spring in the two cases?

(ii) If the mass in figure (a) and the two masses in fig. (b) are released free. What is the period of oscillation in each case?

**Question 15- **A particle of mass 0.1 kg has an initial speed of 4 \(ms^{-1}\) at a point A on a rough horizontal road. The coefficient of friction between the object and the road is 0.15. The particle moves to a point B, at a distance of 2 m from A. What is the speed of the particle at B? (Take g = 10 \(ms^{-2}\))

**Question 16- **A rocket is fired from the earth towards the sun. At what distance from the earth’s centre is the gravitational force on the rocket zero?

**Question 17- **What is the effect of internal and external forces on the velocity of centre of mass.

**Question 18- **Figure below corresponds to two circular motions. The radius of the circle, the period of revolution, the initial position, and the sense of revolution (i.e. clockwise or anticlockwise) are indicated on each figure. Obtain the corresponding simple harmonic motion of the x-projection of the radius vector of the revolving particle P, in each case.

**Question 19- **(i) In deriving the Bernoulli equation, we equated the work done on the fluid in the tube to its change in the potential and kinetic energy. (a) How does the pressure change as the fluid moves along the tube if dissipative forces are present?

(ii) Do the dissipative forces become more important as the fluid velocity increases? Discuss qualitatively.

**Question 20- **A particle has displacement equations

Which of them has uniform acceleration?

**Question 21- **In which of these cases, a body can be considered as point object:

(a) a train moving without jerks between two stations.

(b) a monkey sitting on top of a man cycling smoothly on a circular track.

(c) a spinning cricket ball turns sharply on hitting the ground.

(d) a tumbling beakel slipped off the edge of a table.

**Question 22- **Answer the following question based on the P-T phase diagram of \(CO_{2}\)?

(i) At what temperature and pressure can the solid, liquid and vapour phases of \(CO_{2}\) co-exist in equilibrium?

(ii) What is the effect of decrease of pressure on the fusion and boiling point of \(CO_{2}\).

(iii) What are the critical temperature and pressure for \(CO_{2}\)? What is their significance?

(iv) Is \(CO_{2}\), liquid or gas at-

- \(-70 ^{\circ}C\) under 1 atm.
- \(-60 ^{\circ}C\) under 10 atm.
- \(15 ^{\circ}C\) under 56 atm.