6th Chapter Solved Exercise MCQs Of FSc First Year Physics

Sixth Chapter Solved Exercise MCQs of FSc First Year Physics is a helpful resource for students preparing for exams, featuring solved multiple-choice questions. Each MCQ comes with a clear explanation, making it easier to understand the correct answers. Use this resource to enhance your studies and feel ready for your exams.

Sixth chapter solved MCQs with explanation

1. If the radius of a falling body is doubled, what will be the effect on its terminal velocity?

(a) Increases by 2 times

(b) Decreases by 2 times

(c) Increases by 4 times

(d) Decreases by 4 times

Explanation: Option (c) is correct: Terrminal velocity is proportional to the square of the radius. Doubling the radius increases the terminal velocity by a factor of 2^2 = 4.

2. A ten-meter high tank is full of water. A hole appears at its middle. The speed of efflux will be:

(a) 5 m/s

(b)10 m/s

(c) 100 m/s

(d) 5.11 m/s

Explanation: Option (d) is correct: The speed of efflux from a hole in a tank is given by Torricelli’s theorem, which states that the speed is equal to the square root of 2gh, where g is the acceleration due to gravity and h is the height of the fluid above the hole. Plugging in the values, we get 5.11 m/s.  

3. The maximum drag force of a falling sphere is 9.8 N. Its real weight is:

(a) 4 N

(b) 9.8 N

(c)  0 N

(d)0.0 N

Explanation: Option (b) is correct: When a falling object reaches its terminal velocity, the drag force equals its weight. Therefore, the real weight of the sphere is 9.8 N.

4. The effect of a decrease in pressure with increase in speed of the fluid in a horizontal tube is known as:

(a) Bernoulli’s effect

(b) Torricelli’s theorem

(c)Viscosity effect

(d) Equation of continuit

Explanation: Option (a) is correct: Bernoulli’s equation relates the pressure, velocity, and height of a fluid. It states that as the velocity of a fluid increases, its pressure decreases. This is known as the Bernoulli effect.

5. The SI unit of flow rate is:

(a) m²/s

(b) m/s

(c) m³/s

(d) m³/s

Explanation: Option (c) is correct: Flow rate is the volume of fluid passing through a cross-section per unit time. Therefore, its SI unit is cubic meters per second (m³/s).

6. When the temperature increases, the viscosity of the gases:

(a) Decreases

(b) Increases

(c) Remains constant

(d) None of these

Explanation: Option (b) is correct: When the temperature increases, the viscosity of gases. In gases, higher temperatures lead to more molecular motion and increased collisions between molecules. This results in greater momentum transfer and thus higher viscosity.

7. “Dynamic lift” is related to:

(a) Bernoulli’s theorem

(b)Archimedes’ principle

(c) Equation of continuity

(d) Pascal’s law

Explanation: Option (a) is correct:  Dynamic lift, such as that experienced by an airplane wing, is a direct result of Bernoulli’s principle. The faster-moving air over the top of the wing creates a lower pressure than the slower-moving air below, resulting in an upward force.

8. A gale (i.e., very strong wind) blows over a house. The force due to the gale on the roof is:

(a) In the downward direction

(b) In the upward direction

(c) Zero  

(d) Horizontal

Explanation: Option (d) is correct: The force due to the wind on a roof is primarily horizontal, as the wind is blowing parallel to the roof surface.

9. With increase in temperature, the viscosity of:

(a) A gas increases and a liquid decreases

(b) A gas decreases and a liquid increases

(c) Both gas and liquid increase

(d) Both gas and liquid decreases

Explanation: Option (a) is correct: Increases with temperature Decreases with pressure Increases with molecular weight and shape

10. The viscous drag on a small sphere moving with a speed v is proportional to:

(a) v

(b) v

(c) v²

(d) 1/√v

Explanation: Option (a) is correct: Stokes’ law states that the viscous drag force on a small sphere moving through a fluid is proportional to the velocity of the sphere.

11. Two fog droplets have radius of 2:3. Their terminal velocities are:

(a) 4:9

(b) 4:6

(c) 2:3

(d) 3:2

Explanation: Option (a) is correct: Terminal velocity is proportional to the square of the radius. Therefore, the ratio of the terminal velocities of the two droplets is (2/3)^2 = 4/9.

12. Which one is the venturi relation?

(a)  P₁ – P₂ = ½ρv₁² – ½ρv₂²

(b) V₂ = √(2g(h₁ – h₂))

(c) V₂ = 2g(h₁ – h₂)

(d) None of these

Explanation: Option (a) is correct: The Venturi relation is an equation that relates the pressure difference between two points in a pipe to the velocity difference between those points.

13. Laminar flow usually occurs at:

(a)  High speed

(b) Low speed

(c) Very high speed

(d) None of these

Explanation: Option (b) is correct: Laminar flow is characterized by smooth, parallel streamlines. It typically occurs at low speeds, where the fluid particles do not mix significantly.

14. High concentration of red blood cells increases the viscosity of blood from

(a) 2-3 times that of water

(b) 3-5 times that of water

(c) 2-4 times that of water

(d) 5-7 times that of water

Explanation: Option (b) is correct: Blood is a non-Newtonian fluid, and its viscosity increases with the concentration of red blood cells. A high concentration of red blood cells can increase the viscosity of blood by 3-5 times that of water.

15. For which position, will the maximum blood pressure in the body have the smallest value

(a) Standing up right

(b) Lying horizontally

(c) Standing on one’s head

(d) Sitting relaxed

Explanation: Option (b) is correct: The maximum blood pressure in the body is typically found in the arteries leading from the heart. When lying horizontally, the hydrostatic pressure due to the weight of the blood column is minimized, resulting in a lower maximum blood pressure.

16. The S.I. unit of co-efficient of viscosity is

(a) Kgm⁻¹s⁻¹

(b) Kgm⁻¹s⁻²

(c) Nsm⁻²

(d) Both b & c

Explanation: Option (c) is correct: The coefficient of viscosity relates the shear stress in a fluid to the rate of strain. Its SI unit is either Kgm⁻¹s⁻² or Nsm⁻².

17. The relation between Nm² and torr is

(a) 1 torr = 13.33 Nm²

(b) 1 torr = 133.3 Nm²

(c) 1 torr = 1333.0 Nm²

(d) 1 torr = 1.333 Nm²

Explanation: Option (b) is correct: 1 torr is equivalent to 133.322 Pascals, which is equal to 133.322 Nm².

18. For which position, will the maximum blood pressure in the body have the smallest value

(a)Standing up right

(b) Lying horizontally

(c) Standing on one’s head

(d) Sitting relaxed

Explanation: Option (b) is correct: The maximum blood pressure in the body is typically found in the arteries leading from the heart. When lying horizontally, the hydrostatic pressure due to the weight of the blood column is minimized, resulting in a lower maximum blood pressure.

19. The value of blood pressure with age.   

(a)Increases

(b)Decreases

(c)Remains same

(d)None of these

Explanation: Option (a) is correct:  Blood pressure generally increases with age due to factors such as stiffening of the arteries and reduced elasticity of the heart.

20) Sphygmomanometer is used to measure

(a) Fluid speed

(b) Blood pressure

(c) Blood density

(d) Both b & c

Explanation: Option (b) is correct: A sphygmomanometer is a medical device used to measure blood pressure. It does not measure fluid speed or blood density.