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Physics XI CBSE Half-Yearly Examination 2024
Total Marks: 60
Time: 3 Hours
Section A: Multiple Choice Questions (15 Marks)
Answer all 15 questions. Each question carries 1 mark.
1. A car accelerates uniformly from 10 m/s to 30 m/s in 10 seconds. What is the acceleration of the car?
- (A) 2 m/s²
- (B) 3 m/s²
- (C) 4 m/s²
- (D) 5 m/s²
2. A particle moves along a straight line with uniform velocity. Which of the following statements is correct?
- (A) Its acceleration is non-zero.
- (B) Its speed decreases over time.
- (C) Its velocity is constant.
- (D) It covers unequal distances in equal intervals of time.
3. A body is projected horizontally from a height of 20 m. If the initial velocity is 5 m/s, what is the time taken to reach the ground? (Take $g = 9.8 \, \text{m/s}^2$)
- (A) 2 s
- (B) 4 s
- (C) 3 s
- (D) 5 s
4. The dimensional formula of power is:
- (A) $[MLT^{-2}]$
- (B) $[ML^2T^{-2}]$
- (C) $[ML^2T^{-3}]$
- (D) $[ML^3T^{-2}]$
5. Which of the following is not a vector quantity?
- (A) Displacement
- (B) Velocity
- (C) Speed
- (D) Acceleration
6. A force of 10 N is applied to a block of mass 2 kg on a frictionless surface. What is the acceleration of the block?
- (A) 5 m/s²
- (B) 10 m/s²
- (C) 20 m/s²
- (D) 2 m/s²
7. If a particle is moving in a circular path with constant speed, then:
- (A) Its velocity is constant.
- (B) Its acceleration is zero.
- (C) Its direction changes continuously.
- (D) Its kinetic energy is zero.
8. A force of 50 N acts on a body at an angle of 30° with the horizontal. What is the horizontal component of this force?
- (A) 25 N
- (B) 50 N
- (C) 43.3 N
- (D) 0 N
9. The unit of work in the SI system is:
- (A) Newton
- (B) Joule
- (C) Watt
- (D) Pascal
10. If the speed of an object is doubled, its kinetic energy becomes:
- (A) Half
- (B) Double
- (C) Four times
- (D) Unchanged
11. A bullet of mass 0.01 kg is fired with a velocity of 100 m/s. What is its kinetic energy?
- (A) 50 J
- (B) 100 J
- (C) 5 J
- (D) 500 J
12. The slope of a velocity-time graph gives:
- (A) Speed
- (B) Acceleration
- (C) Displacement
- (D) Momentum
13. Which of the following has the same dimensional formula as energy?
- (A) Force
- (B) Power
- (C) Work
- (D) Velocity
14. A body of mass 5 kg is moving with a velocity of 2 m/s. Its momentum is:
- (A) 5 kg m/s
- (B) 10 kg m/s
- (C) 15 kg m/s
- (D) 20 kg m/s
15. The force of friction between two surfaces does not depend on:
- (A) Nature of surfaces
- (B) Area of contact
- (C) Normal reaction
- (D) Relative motion
Section B: Assertion and Reasoning (Any 2)(2 Marks)
Answer all 3 questions. Each question carries 1 mark.
16. Assertion: When a body falls freely under gravity, its acceleration remains constant.
Reason: The acceleration due to gravity on the surface of the Earth is a constant.
- (A) Both Assertion and Reason are true, and Reason is the correct explanation of Assertion.
- (B) Both Assertion and Reason are true, but Reason is not the correct explanation of Assertion.
- (C) Assertion is true, but Reason is false.
- (D) Assertion is false, but Reason is true.
17. Assertion: A heavy body and a light body fall at the same rate in the absence of air resistance.
Reason: In the absence of air resistance, the acceleration due to gravity is the same for all objects.
- (A) Both Assertion and Reason are true, and Reason is the correct explanation of Assertion.
- (B) Both Assertion and Reason are true, but Reason is not the correct explanation of Assertion.
- (C) Assertion is true, but Reason is false.
- (D) Assertion is false, but Reason is true.
18. Assertion: A moving body can have zero momentum.
Reason: A body moving with constant speed in a straight line has constant momentum.
- (A) Both Assertion and Reason are true, and Reason is the correct explanation of Assertion.
- (B) Both Assertion and Reason are true, but Reason is not the correct explanation of Assertion.
- (C) Assertion is true, but Reason is false.
- (D) Assertion is false, but Reason is true.
Section C: Short Answer Questions (10 Marks)
Answer all 5 questions. Each question carries 2 marks.
19. Define linear momentum. Write its SI unit and explain its significance.
20. State Newton's second law of motion and derive the relation $F = ma$.
21. Explain the law of conservation of linear momentum with an example.
22. A car of mass 1000 kg is moving with a speed of 30 m/s. Calculate its kinetic energy.
23. What is the difference between speed and velocity? Give one example of each.
Section D: Long Answer Questions (12 Marks)
Answer any 3 out of 4 questions. Each question carries 4 marks.
24. Derive the equation of motion for a uniformly accelerated body using graphical method.
25. State and prove the work-energy theorem for a variable force.
26. Discuss the motion of a projectile. Derive expressions for the maximum height and range of the projectile.
27. What is centripetal force? Derive an expression for centripetal force acting on a body moving in a circular path.
Section E: Very Long Answer Questions (15 Marks)
Answer any 3 out of 5 questions. Each question carries 5 marks.
28. What is the principle of conservation of mechanical energy? Derive an expression for the conservation of mechanical energy in the case of a freely falling body under gravity.
29. Discuss the different types of friction. How can we reduce friction in machines? Give relevant examples.
30. Derive the expression for the potential energy of a body placed at a height \( h \) above the ground. How does this energy change as the body falls freely under gravity?
31. Explain the concept of work done by a variable force. Derive the work done by a variable force using integration, considering a force acting along a straight line.
32. State and explain the principle of conservation of linear momentum. Discuss how this principle is used in the analysis of collisions. Provide examples.
Section F: Case-Based Questions (6 Marks)
Read the case study carefully and answer the questions that follow. Each question carries 4 marks.
33. Case Study 1: A block of mass 2 kg is placed on a frictionless horizontal surface. A constant horizontal force of 10 N is applied to the block.
(a) Calculate the acceleration of the block.
(b) If the force is applied for 5 seconds, find the final velocity of the block.
(c) What is the distance covered by the block in 5 seconds?
(d) Discuss the energy transformation occurring during this motion.
34. Case Study 2: A car of mass 1500 kg is traveling at a speed of 20 m/s. The driver suddenly applies brakes, and the car comes to rest after traveling a distance of 50 m.
(a) What is the initial kinetic energy of the car?
(b) Calculate the work done by the brakes to bring the car to rest.
(c) Determine the average retarding force applied by the brakes.
(d) Explain the principle of energy conservation in the context of this situation.
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