Kerala Plus One Physics Question Paper March 2020 with Answers

Reviewing Kerala Syllabus Plus One Physics Previous Year Question Papers and Answers Pdf March 2020 helps in understanding answer patterns.

Kerala Plus One Physics Previous Year Question Paper March 2020

Time: 2 Hours
Total Scores: 60

Answer any 4 questions from 1 to 5. (4 × 1 = 4)

Question 1.
Which of the following fundamental forces binds protons and neutrons in a nucleus?
(a) Gravitational force
(b) Electro-magnetic force
(c) Strong nuclear force
(d) Weak nuclear force
Answer:
(c) Strong nuclear force

Question 2.
Four pairs of initial and final positions of a body along an x-axis are given. Which pair gives a positive displacement of the body?
(a) -10 m, +15 m
(b) -5 m, -12 m
(c) 2 m, -5 m
(d) 2 m, 1 m
Answer:
(a) -10 m, +15 m

Question 3.
Newton’s first law of motion describes the ________________
(a) Energy
(b) Work
(c) Inertia
(d) Momentum
Answer:
(c) Inertia

Question 4.
The rotational analog of force is ________________
Answer:
torque

Question 5.
The Young’s modulus of rubber is ________________
(a) Greater than that of steel
(b) Less than that of steel
(c) Equal to that of steel
Answer:
(b) Less than that of steel

Answer any 8 questions from 6 to 15. Each carries 2 scores. (8 × 2 = 16)

Question 6.
The centripetal force on a body of mass ‘m’ and velocity ‘v’ moving in a circular orbit of radius ‘r’ is given by F = \(\frac{m v^2}{r}\).
(a) Write the dimensional formula of force.
(b) Using the formula of centripetal force write an equation to find percentage error in centripetal force.
Answer:

Question 7.
State the law of conservation of linear momentum.
Answer:
If the total force acting on a body is zero, its linear momentum will be a constant.

Question 8.
Find out the signs of work done in the following cases:
(a) Work done by a man in lifting a bucket out of a well.
(b) Work done by friction on a body sliding down an inclined plane.
(c) Work done by an applied force on a moving on a rough horizontal plane.
(d) Work done by the resistive force of air on a vibrating pendulum
Answer:
(a) Positive work done
(b) Negative work done
(c) Positive work done
(d) Negative work done

Question 9.
A cord of negligible mass is wound around the rim of a flywheel mounted on a horizontal axle as shown in the figure:

Calculate the angular acceleration of the wheel if a steady pull of 25 N is applied to the cord. Moment of inertia of flywheel about its axis = \(\frac{\mathrm{MR}^2}{2}\).
Answer:

Question 10.
The escape speed of an object from the Earth is 11.2 km/s.
(a) Define the escape speed of an object.
(b) How escape speed is related to the mass of the object?
Answer:
(a) The minimum speed required for an object to escape from earth’s gravitational attraction is called escape speed.
(b) Escape speed is independent of the mass of an object.

Question 11.
Beams of different cross-sectional shapes are shown in the figure.

Why the beam B used in the construction of bridges?
Answer:
We can avoid buckling when we use the beam B.

Question 12.
The given figure shows the principle behind the hydraulic lift.

The radius of the small piston is 5.0 cm. and that of the larger piston is 15 cm. Calculate the force F, if the mass of the car to be lifted is 1350 kg (g = 9.8 ms^-2).
Answer:
Radius of piston r₁ = 5 × 10^-2 m
Radius of second piston r₂ = 15 × 10^-2 m
Force on the second piston F₂ = 1350 × 10 = 13500 N

Question 13.
What do you mean by capillary rise? What is the phenomenon responsible for it?
Answer:
When a capillary tube is dipped in a liquid, the liquid rises in the tube. This phenomena is called capillary rise. Surface tension is the reason forthe  capillary rise.

Question 14.
Show that the function (sin ωt – cos ωt) represents simple harmonic motion.
Answer:

The above equation represents S.H.M.

Question 15.
A steel wire has a length of 12.0 m and a mass of 2.10 kg. What is the tension in the wire if the speed of a transverse wave on the wire is 343 ms^-1?
Answer:
Length l = 12 m
Mass m = 2.10 kg
Speed v = 343 m/s
Mass per unit length μ = \(\frac{m}{\ell}=\frac{2.10}{12}\) = 0.175 kg/m
Velocity v = \(\sqrt{\frac{T}{\mu}}\)
∴ τ = v²μ
= (343)² × 0.175
= 2.05 × 10⁴ N

Answer any 6 questions from 16 to 23. Each carries 3 scores. (6 × 3 = 18)

Question 16.
The volume of water flowing out through a pipe in a given time is V = KA²ut, where A is the area of the cross-section of the pipe, u is the speed of flow, t is the time and K is a dimensionless constant.
(a) Name the principle that can be used to check the dimensional correctness of this equation.
(b) Check the correctness of the equation. (1 + 2)
Answer:
(a) Principle of homogeneity
(b) Dimension of v = L³
Dimension of A = L²
Dimension of u = LT^-1
Dimension of t = T
ie., the given equation,
V = KA²ut
M⁰L³L⁰ = (L²)² (LT^-1)T
⁰L³T⁰ = L⁴L¹
L³ = L⁵
Dimension of LHS ≠ Dimension of R.H.S
Hence this equation is wrong.

Question 17.
The position vector r of a particle P located in an xy-plane is shown in the figure. (1 + 1 + 1)

(a) Redraw the figure by showing the rectangular components.
(b) Write the position vector in terms of rectangular components.
(c) Write an equation to find the magnitude of the resultant of two vectors A and B.
Answer:

Question 18.
Gaphs of the potential energy, kinetic energy, and total energy of an oscillating spring are shown in the figure. (1½ + 1½)

(a) Find out the potential energy, kinetic energy, and total energy from the graph.
(b) Derive an expression to find the potential energy of a spring.
Answer:
(a) Potential energy – B
Kinetic energy – C
Total energy – A
(b)

Consider a massless spring fixed to a rigid support at one end and a body attached to the other end. The body moves on a frictionless surface.
If a body is displaced by a distance dx, The work done for this displacement dw = Fdx
∴ Total work done to move the body from x = 0 to x

Question 19.
Observe the given figure. (1 + 2)

(a) Is this a heat engine or refrigerator?
(b) Write the 4 steps of operation in the Carnot cycle.
Answer:
(a) Heat engine
(b) Isothermal expansion, Adiabatic expansion
Isothermal compression, Adiabatic compression

Question 20.
A refrigerator is to maintain eatables kept inside at 9°C. If room temperature is 36°C, calculate the coefficient of performance.
Answer:
Coefficient of performance

Question 21.
Prove that the average kinetic energy of a molecule is proportional to the absolute temperature of the gas.
Answer:

Question 22.
Simple harmonic motion of a block of mass m attached to a spring is shown in figure. The distance between extreme points A and B is 10 cm.

Take the direction from A to B as the positive. Redraw the given table and give the signs of velocity, acceleration, and force.

Answer:

Question 23.
A transverse harmonic wave on a string is described by y(x, t) = 3.0 sin(36t + 0.018x + π/4) where x and y are in cm and t in s. (½ + 1 + ½ + 1)
(a) Is this a traveling wave or a stationary wave?
(b) What are its amplitude and frequency?
(c) What is the initial phase at the origin?
(d) What is the least distance between two successive crests in the wave?
Answer:
(a) Travelling wave
(b) Amplitude A = 3 m
ωt = 36t
ω = 36
2πf = 36
Frequency, f = \(\frac{36}{2 \pi}\) = 5.7 Hz
(c) Initial phase = π/4
(d) k = 2π/λ
λ = \(\frac{2 \pi}{k}\) ………(1)
fre equation kx = 0.018x
k = 0.018
Sub (2) in (2), we get,
λ = \(\frac{2 \pi}{0.018}\) = 348.9 cm

Answer any 3 questions from 24 to 27. Each carries 4 scores. (3 × 4 = 12)

Question 24.
Velocity-time graph of a ball thrown vertically upwards with an initial velocity is shown in the figure. (1 + 1½ + 1½)

(a) What is the magnitude of the initial velocity of the ball?
(b) Calculate the distance traveled by the ball during 20 s, from the graph.
(c) Calculate the acceleration of the ball from the graph.
Answer:
(a) Initial velocity v = 100 m/s
(b) Distance = Area of graph
= \(\frac{1}{2}\) × b₁h₁ + \(\frac{1}{2}\) × b₂h₂
= \(\frac{1}{2}\) × 100 × 10 + \(\frac{1}{2}\) × 100 × 10
= 1000 m
(c) Slope gives acceleration
Slope = \(\frac{\Delta v}{\Delta t}\)
= \(\frac{0-100}{10-0}\)
= -10 m/s²

Question 25.
The figure shows three paths for a football kicked from ground level with the same velocity. Ignore the effects of air resistance.

(a) Derive an equation for the maximum height of this football.
(b) In which path the horizontal component of velocity is maximum? (3 + 1)
Answer:
(a) The vertical height of the body is decided by the vertical component of velocity (u sin θ).
The vertical displacement of the projectile can be found using the formula v² = u² + 2as
When we substitute v = 0, a = -g, s = H and u = u sin θ, we get
0 = (u sin θ)² + 2 × -g × H
⇒ 2gH = u²sin²θ
⇒ H = \(\frac{u^2 \sin ^2 \theta}{2 g}\)
(b) Ball 3 has maximum horizontal velocity. This ball travels a maximum horizontal distance.

Question 26.
State theorem of perpendicular axes on the moment of inertia. Derive an expression to find the moment of inertia of a circular disc about one of its diameters with the help of a neat diagram.
Answer:
The moment of inertia about the z-axis is equal to the sum of the moment of inertia about the x-axis and y-axis. If planer lamina lies in xy-plane.

According to the perpendicular axis theory
I_z = I_x + I_y
⇒ \(\frac{M R^2}{2}=2 I_x\)
⇒ Ix = \(\frac{\mathrm{MR}^2}{4}\)
Where Ix is the moment of inertia about the diameter of a disc.

Question 27.
Temperature is the degree of hotness of a body.
(a) The temperature of a normal human body is 98.6 °F. What is the corresponding temperature in the Celsius scale?
(b) Define latent heat.
(c) Why does a brass tumbler feel much colder than a wooden tray on a chilly day? (2 + 1 + 1)
Answer:
(a) \(\frac{C}{100}=\frac{F-32}{180}\)
⇒ C = \(\left(\frac{98.6-32}{180}\right) \times 100\) = 37°C
(b) Latent heat is the energy required to convert one form of substance into another form.
(c) Brass is a metal, which conducts heat energy more easily than wood. Hence it feels much colder than a wooden tray.

Answer any 2 questions from 28 to 30. Each carries 5 scores. (2 × 5 = 10)

Question 28.
The circular motion of a car on a banked road is shown in the figure.

(a) Write the names of forces A, B, C, and D in the figure.
(b) Write the equation which equates forces on the car along the horizontal and vertical directions.
(c) State the law of static friction. (2 + 2 + 1)
Answer:
(a) A – Normal reaction
B – weight of the body
C – Centripetal force
D – Force due to friction
(b) Various horizontal and vertical forces acting on the body are shown in the figure.

from the figure we get
N sin θ + f_s cos θ = \(\frac{m v^2}{r}\)
N cos θ = f_s sin θ + mg
(b) Laws of Static Friction:

• The force of maximum static friction is directly proportional to the normal reaction.
• The force of static friction is opposite to the direction in which the body tends to move.
• The force of static friction is parallel to the surfaces in contact.
• The force of maximum static friction is independent of the area of contact (as long as the normal reaction remains constant).
• The force of static friction depends only on the nature of surfaces in contact.

Question 29.
(a) Choose the correct alternative:
(i) Acceleration due to gravity increases/decreases with increasing altitude.
(ii) Acceleration due to gravity increases/decreases with increasing depth.
(iii) The total energy of an orbiting satellite is negative of its kinetic/potential energy.
(iv) The polar satellite goes around the earth in a north-south direction/east-west direction.
(b) State Kepler’s law of periods.
Answer:
(a) (i) decreases
(ii) decreases
(iii) kinetic energy
(iv) north-south direction
(b) The square of the period of revolution of a planet is proportional to the cube of the semi-major axis of the ellipse traced out by the planet.
∴ T² ∝ a³
a is the semi-major axis.

Question 30.
Consider a fluid moving in a pipe of varying cross-sectional area as shown in figures a₁, a₂ are cross-sectional areas of pipe and v₁, v₂ are the velocities of fluid.

(a) State Bernoulli’s principle.
(b) Derive Bernoulli’s equation.
(c) Write the equation of Stake’s law. (1 + 3 + 1)
Answer:
(a) The total energy of an incompressible non-viscous liquid flowing form one place to another without friction is a constant.
(b) Proof

Consider an incompressible liquid flowing through a tube of non-uniform cross-section from region 1 to region 2.
Let P₁ be the pressure, A₁ the area of the cross-section, and V₁ the speed of flow at region 1.
The corresponding values in Region 2 are P₂, A₂, and V₂ respectively.
Region 1 is at a height of h₁ and region 2 is at a height of h₂.
The work done on the liquid in a time Δt at region 1 is given by
W₁ = P₁ΔV₁
Similarly, the work done in a time Δt at region 2 is given by
W₂ = -P₂ΔV₂
Net workdone ΔW = P₁ΔV₁ – P₂ΔV₂
According to the equation of continuity
ΔV₁ = ΔV₂ = ΔV
ΔW = P₁ΔV – P₂ΔV
ΔW = (P₁ – P₂) ΔV …………(1)
This work changes the kinetic energy, pres-sure energy, and potential energy of the fluid.
If Δm is the mass of liquid passing through the pipe in a time Δt.
the change in Kinetic energy is given by
Δk.E = \(\frac{1}{2} \Delta m V_2^2-\frac{1}{2} \Delta m V_1^2\) ……..(2)
Change in gravitational potential energy is given by
ΔP.E = Δmgh₂ – Δmgh₁ ………(3)
According to the work-energy theorem work done is equal to the change in kinetic energy plus the change in potential energy.
ie; Δw = ΔkE + ΔPE ………..(4)
Substituting eq. 1,2 and 3 in eq. 4, we get
\(P_1+\frac{1}{2} \rho V_1^2+\rho \mathrm{gh}_1=\mathrm{P}_2+\frac{1}{2} \rho V_2^2+\rho \mathrm{gh}_2\) ……….(5)
∴ \(P+\frac{1}{2} \rho V^2+\rho g h\) = a constant.
(c) F = 6πηav