**9th CBSE Science Examination: Mid Term Question Paper (2019-20)**

**School Name: Himalaya Public School**, Sector 13, Rohini,

**Delhi**110085

**India**

**Time:**3 Hrs.

**Marks:**70

**Class: 9th**

**Date: 17/9/2019**

**Subject: Science**

**General Instructions:**

- All questions are compulsory. There are 37 questions in all.
- This question paper has four sections.
**Section A, Section B, Section C and Section D.** **Section A**contains**20 questions**of**one mark**each,**Section B**contains**7 questions**of marks each,**Section C**contains**7 questions**of**3 marks**each and**Section D**contains**3 questions**of**5 marks**each.- There is no overall choice. However an internal choices have been provided in 1 question of 2 marks, 2 questions of 3 marks each and all the questions of 5 marks. You have to attempt only one of the choices in such questions.

**Section A**

#### Question: 1. What do you understand by EM force?

#### Question: 2. What LASER stands for?

#### Question: 3. Deduce the dimensional formula for (i) Potential Difference, (ii) Energy

#### Question: 4. State the number of significant figures in the following: (i). 050 cm, (ii) 5300 kg.

#### Question: 5. What does the following graph signify? Is it possible or not?

#### Question: 6. Can a body have a constant speed and still have varying velocity?

#### Question: 7. The displacement of a body is given to be proportional to the cube of time elapsed. What is the nature of the acceleration of the body?

#### Question: 8. When is the magnitude of the resultant of the vectors equal to either of them?

**9th CBSE Science Examination – Question**: 9. What is the angle between

#### Question: 10. Name the quantity which remains unchanged during the flight of an oblique projectile?

#### Question: 11. Explain why sand is thrown on tracks covered with snow in hilly areas?

#### Question: 12. The motion of a particle of mass on is described by y = ut + ½ gt^{2}. Find the force acting on the particle?

#### Question: 13. A ship of Mass 3×10^{7 }kg initially at rest is pulled by a force of 5×10^{4 }N, through a distance of 3m. Assuming that the resistance due to water is negligible the speed of the ship is

- 1.5 m/s
- 60 m/s
- 0.1 m/s
- 5 m/s

#### Question: 14. Two astronauts on the surface of the moon cannot talk to each other. Why?

#### Question: 15. If the pressure of a gas constant temperature is increased four time, how how the velocity of sound in the gas will be affected?

#### Question: 16. A girl is swinging in a swing in a sitting position. How will the period of the swing be affected if she stands up?

**9th CBSE Science Examination – **Question: 17. Why a loud sound is heard at Resonance?

#### Question: 18. Which one of the following pairs of quantities has the same dimension?

- Force and work done
- Momentum and impulse
- Pressure and force
- Surface tension and stress

#### Question: 19. A particle is thrown above, then correct vt graph will be

#### Question: 20. Define dimensionless constants with examples (two).

**Section B**

#### Question: 21. Differentiate between weak nuclear and strong nuclear forces.

#### Question: 22. Derive 2nd and 3rd equation of motion using integral calculus.

#### Question: 23. A ball is released from the top of a tower of height h metres. If takes T seconds to reach the ground. What is the position of the ball in T/3 seconds.

#### Question: 24. Two vectors

#### are mutually perpendicular to each other. What is the value of α?

#### OR

#### State parallelogram Law of vector addition with proof.

#### Question: 25. State the law of conservation of linear momentum and derive it from Newton’s 2nd Law of Motion?

#### Question: 26. A SHM is represented by y=5 sin (20*t* + 0.5)*m*. What are its amplitude, angular frequency and time period.

#### Question: 27. Derive Newton’s formula for the velocity of sound in air, what was the Laplace correction applied.

**Section C**

#### Question: 28. The period of vibration of a tuning fork depends on the length ‘*l*‘ of its prong, density ‘d’ and Young’s modulus ‘Y’ of its material. Deduce the expression for the period of vibration on the basis of dimensions.

#### OR

#### The specific resistance σ of a thin wire of radius r cm, resistance RΩ and length L cm given by σ = 8πr²R/L

#### If r = 0.26 + 0.02 cm

#### R = 32 + 1Ω

#### And L = 78 + 0.01 cm

#### Also find % error in σ.

#### Question: 29. A ball thrown vertically upwards with a speed of 19.6 m/s from the top of a tower returns to the earth in 6 sec. Find the height of the tower.

#### Question: 30. Define angular displacement. Deduce the relation of angular acceleration with linear acceleration.

#### Question: 31. A body of mass m is suspended by two strings making angles α and β with the horizontal as shown in fig. Find the tensions in the string.

#### OR

#### Find the expression for the work done in sliding the body over a rough horizontal surface.

#### Question: 32. Why does a cyclist lean inwards when moving along a curved path? Determine the angle through which a cyclist bends from the vertical while negotiating a curve.

#### Question: 33. Derive the expression for the oscillations of Mass attached with a vertical spring.

#### Question: 34. Derive the expression for the energy of a particle executing SHM. Also plot the graph showing the variation of P.E., K.E. and T.E. (total energy) of particle executing SHM.

**Section D**

#### Question: 35. A man of Mass *m* is standing on the floor of a lift. Find his apparent weight when the lift is

#### (i) moving upwards with uniform acceleration a (ii) moving downwards with uniform acceleration, a (ii) at rest or moving with uniform velocity, V(iv) falling freely.

#### OR

#### Define friction and its types. Explain with labelled variation between friction (f) and applied Force (F). Derive the expression for coefficient of static friction.

#### Question: 36. Define phase and phase difference. Plot the sinusoidal variation and give phasor treatment to the wave.

#### Y_{1} = α sin *w*t.

#### Y _{1} = α sin (*w*t. + π/2)

#### OR

#### Write equation representing a progressive wave propagating aong positive x-axis.

Differentiate between Longitudinal and transverse wave Motion.

#### Question: 37. In successive measurements, the readings of the period of oscillation of a simple pendulum were found to be 2.635, 2.565, 2.425, 2.715, 2.805 sec in an experiment.

**Calculate:**

- Mean value of the period of oscillation absolute error in each measurement
- Mean absolute error, relative error, percentage error.