## Kerala Plus One Physics Previous Year Question Paper 2017

Time: 2 Hours

Cool off time: 15 Minutes

Maximum: 60 Scores

General Instructions to candidates

- There is a ‘cool off time’ of 15 minutes in addition to the writing time.
- Use the ‘cool off time’ to get familiar with the questions and to plan your answers.
- Read the instructions carefully.
- Read questions carefully before you answering.
- Calculations, figures, and graphs should be shown in the answer sheet itself.
- Malayalam version of the questions is also provided.
- Give equations wherever necessary.
- Electronic devices except non-programmable calculators are not allowed in the Examination Hall.

Question 1.

Pick the odd one out among the following forces:

a. Gravitational force

b. Weak nuclear force

c. Viscous force

d. Electromagnetic force

Question 2.

The demonstration of conservation of angular momentum is schematically shown in the figures.

Identify the figure which has more angular velocity.

Question 3.

“Two systems in thermal equilibrium with a third system, are in thermal equilibrium with each other”. Identify the law given by the above statement.

Question 4.

A steel rod has a radius of 10 mm and a length of 1.0 m. A 100 kN force stretches it along its length. Calculate the elongation of the steel rod. [Young’s modulus of steel is 2.0 × 10^{11} N/m^{2}.]

OR

A metal cube of side 10 cm is subjected to a; shear stress 10^{4} N/m^{2}. Calculate the rigidity: modulus, if the top of the cube is displaced by 0.05 cm with respect to its bottom.

Question 5.

Draw the schematic diagram of a hydraulic lift. Give its working principle.

Question 6.

Estimate the average thermal energy of the helium atom at a temperature of 27°C. [Boltzmann constant is 1.38 × 10^{-23}J/K.]

Question 7.

The graph below exhibits the anomalous expansion of water.

Based on the graph, explain how lakes freeze from the top to bottom rather than from bottom to top.

Question 8.

Match the following in three columns.

Question 9.

a. The figure below shows the ‘parallax method’ to measure the distance ‘D’ of a planet ‘S’ from the earth.

Mark the parallax angle ‘0’ in the figure. Explain how the distance ‘D’ can be measured.

b. Check whether the equation mv^{2} = mgh is dimensionally consistent. Based on the above equation, justify the following statement. “A dimensionally correct equation need not be actually an exact equation”.

Question 10.

a. Choose the correct statement/statements related to uniform circular motion.

i. The acceleration in uniform circular motion is tangential to the circle.

ii. The acceleration in uniform circular motion is directed radially inwards.

iii. The velocity in uniform circular motion has constant magnitude.

iv. The velocity in uniform circular motion is directed radially inwards.

b. A particle is projected up into the air from the point with a speed of 20 m/s at an angle of projection 30°. What is the maximum height reached by it?

Question 11.

a. The escape speed from the surface of the earth is given by …………………..

b. An artificial satellite circulating the earth is at a height 3400 km from the surface of the earth. If the radius of the earth is 6400 km and g = 9.8 m/s^{2}, calculate the orbital velocity of the satellite.

Question 12.

a. Among the following, which are examples of simple harmonic motion?

i. The rotation of the earth about its axis.

ii. Vertical oscillations of a loaded spring.

iii. Oscillations of a simple pendulum.

iv. Uniform circular motion.

b. The displacement in simple harmonic motion can be represented as x(t) = A Cos(ωt+ Φ), where ‘Φ’is the phase constant. Identify and define ‘A’ and ‘co’ in the equation.

Question 13.

a. A transverse harmonic wave is described j by y=3.0 Sin (0.018 × + 36t), where ‘x’ and ‘y’ are in cm. The amplitude of this; the wave is

b. The figure below shows the fundamental mode or first harmonic in a stretched j string when a standing wave is formed ‘ in the string.

Draw the figure that shows the second; harmonic in the string. If ‘L’ is the length of the string and Vis the speed of the: wave in the string, what are the equations of first and second harmonic frequent:

Question 14.

An object released near the surface of the I earth is said to be in free fall. (Neglect the air resistance)

a. Choose the correct alternative from the clues given at the end of the statement. “Free fall is an example of accelerated motion”.

b. The incomplete table shows the velocity (υ) of a freely falling object in a time interval of 1 s. (Take g = 10 m/s^{2})

Complete the table and draw the velocity time graph.

c. Area under velocitytime graph gives.

Question 15.

The schematic diagram of the circular motion of a car on a banked road is shown in the figure.

a. If the centripetal force is provided by the horizontal components of ‘N’ and ‘F’ arrive at an expression for maximum safe speed.

b. The optimum speed of a car on a banked road to avoid wear and tear on its tyres is given by …………….

Question 16.

Energy of a body is defined as its capacity of doing work”.

a. The energy possessed by a body by virtue of motion is known as ………….

b. A body of mass 5 kg initially at rest is subjected to a horizontal force of 20 N. What is the kinetic energy acquired by the body at the end of 10 s?

c. State whether the following statement is TRUE or FALSE. “The change in kinetic energy of a particle is equal to the work done on it by the net force”.

Question 17.

The angular momentum of a particle is the rotational analogue of its linear momentum.

a. The equation connecting angular momentum and linear momentum are ……………

b. Starting from the equation connecting angular momentum and linear momentum, deduce the relation between torque and angular momentum.

Moment of inertia in rotational motion is analogous to mass in linear motion.

a. The moment of inertia of a circular disc about an axis perpendicular to the plane, at the center is given by ………….

b. State perpendicular axis theorem and by using the theorem, deduce the moment of inertia of the circular disc about an axis passing through the diameter.

Question 18.

A region of streamline flow of an incompressible fluid is shown in the figure.

a. By considering mass conservation in the fluid flow, arrive at the ‘equation of continuity’.

b. The onset of turbulence in a fluid is determined by ‘Reynolds number’, given as …………….

Schematic diagram of capillary rise in a narrow tube is shown in the figure.

a. Arrive at an expression for capillary height ‘h’ in terms of the surface tension of the liquid.

b. On the surface of the moon, the liquid in a capillary tube will rise to the ……………..

i. same height as on earth,

ii. less height as on earth

iii. more height than that on earth

iv. infinite height.

Answers

Answer 1.

Viscous force (Not a fundamental force in nature)

Answer 2.

Figure 2. (Law of a moment of inertia) When the man stretched his arm, according to a law of conservation of angular momentum the distance from the axis of rotation increases and

so a moment of inertia increases and thereby angular speed decreases.

Answer 3.

Zeroth law of thermodynamics. 0 .05/10

Answer 4.

OR

Answer 5.

Pascal’s law is the working principle behind the hydraulic lift. Pascal’s law states that The pressure in a fluid at rest is same at all points if we ignore gravity.

If the pressure in a liquid is changed at a particular point, the change is transmitted to the entire liquid without being diminished in magnitude. The pressure exerted at any point on an enclosed liquid is transmitted equally in all directions.

Construction: It is a simple application of Pascal’s law. There are two cylinders C_{1} and C_{2} of cross-sectional areas A_{1} and A_{2} connected by a pipe. Pistons are fitted in both cylinders. The load to be lifted is kept on the platform of the piston with more area (A_{2}>A_{1}). The cylinders and pipe contain a liquid.

Working: A force is applied on the smaller piston. Then pressure exerted on the liquid is, \(P=\frac { { F }_{ 1 } }{ A }\) According to Pascal’s law, the same pressure ‘P’ is transmitted to the larger piston. Force on larger piston ¡s

Hence by making the ratio A_{2}/A_{1} large, very heavy loads like cars can be lifted by using a small force.

Answer 6.

Answer 7.

When water is cooled from 4°C to 0°C, it expands. So ¡ce at 0°C ¡s less dense (more volume) than water at 4°C. When lake starts cooling water at the top reaches 4°C and sinks to the bottom due to high density. This continues till whole water reaches 4°C. Now when the temperature decreases to zero water on the top becomes ice which is less dense than the water below. So it does not sink.

Answer 8.

Answer 9.

To measure the distance D of a faraway planet S by the parallax method, we observe it from two different positions (observatories) A and B on the earth, separated by distance AB = b at the same time as in fig. We measure the angle between the two directions along which the planet is viewed at these two points. The ∠ASB represented by symbol 0 is called the parallax angle or parallactic angle.

As the planet is very far away, \(\frac { { b } }{ D } <<1\) and therefore, O is very small. Then we approxi mately take AB as an arc of length b or a circle with centre at S and the distance D as the radius AS = BS. So that AB = b = DO where O is in radians \(D=\frac { { b } }{ \theta }\)

b. mv^{2} = mgh, takig dimension on both sides

[M] [LT^{-1}]^{2} = [M] [LT^{-1}] [L]

[ML^{2}T^{2}] = [M^{1}L^{2}T^{2}]

The given equation is dimensionally cor rect. This is not the exact equation, which is mgh. Since the fraction ½ has no dimension, the complete consistency can’t be checked.

Answer 10.

Answer 11.

Answer 12.

a. (ii) and (iii)

b. A is the amplitude and w is the angular frequency.

Amplitude is the maximum displacement of the oscillating particle on either side of its mean position. Thus X_{mxv} = + A Angular frequency is equal to the product of the frequency of the body and 27t.

Answer 13.

a. 3 cm

b.Fundamental mode (or) First harmonic If the string is plucked in the middle and released, then it vibrates ¡n one segment with nodes at its ends and an antinode in the middle.

This is the lowest frequency with which string vibrates.

Second harmonic If the string is pressed in the middle and plucked at one-fourth of its length, then the string vibrates in two segments.

Answer 14.

Uniformly.

c. Displacement

Answer 15.

a. To avoid skidding and damage to tires of vehicles, the outer part of a road is slightly raised than the inner part. This is known as banking of roads.

1. The weight of the car vertically downwards.

2. Normal reaction R acting normal to the road.

3. Frictional force acting parallel to the road. Since there is no vertical acceleration,

R cosθ = mg + Fsinθ

or Rcosθ Fsinθ = mg …(1)

Now for maximum speed, F = μ, R

The centripetal force is provided by horizontal components of R and F as shown in the figure.

Answer 16.

Answer 17.

b. This theorem is good for flat bodies which means, thickness much less than length and breadth. The theorem states that “the moment of inertia of a planar body about an axis perpendicular to its plane is equal to the sum of moments of inertia about two mutually perpendicular axes passing through the same point, lying on the plane”. Moment of inertia about diameter can be found using perpendicular axis theorem.

Answer 18.

a. Consider a nonviscous (no internal friction) and incompressible (density constant during flow) liquid flowing steadily between the sections P and R of a pipe of varying cross-section. Let the area of a cross section at P be A, and that at R be A_{2}. Let the speed of fluid be v_{1} at P and v_{2} at R.

As, m = volume × density = area of cross-section × length × density Mass of fluid that flows through P in time Δt, m_{1} = A_{1}v_{1}P_{1} Δt

Mass of fluid that flows through R in time At, m2 = A_{2}V_{2}P_{2} Δt

By conservation of mass, m1 = m_{2}

A_{1}v_{1}P_{1} Δt = A_{2}v_{2}p_{2} Δt and P_{1} = p_{2} (incompressible fluid)

A_{1}v_{1}= A_{2}v_{2}

The product of the area of crosssection and the speed remains the same at all points of a tube of flow. This is called the equation of continuity and expresses the law of conservation of mass in fluid dynamics.

b. iii \(\frac { p\upsilon d }{ n } =Re\)

OR

a. When a clean capillary tube is dipped in a liquid, which wets it, the liquid immediately rises in the tube. This is called capillary rise.

Consider a capillary tube of radius ripped vertically in a liquid of density p and surface tension a. The meniscus of the liquid inside the tube is concave. Thereby the liquid rises through the tube to some height. Let ‘ R’ be the radius of the meniscus, 0 be the angle of contact and h the height of the liquid column in the tube with respect to the level of a liquid outside.

Here the hydrostatic pressure exerted by the liquid column becomes equal to the excess pressure p. Therefore at equilibrium, we have p = hpg

b. iii. more height than that on earth