## Kerala Plus One Physics Previous Year Question Paper 2018

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.

Answer any four questions from question numbers 1 to 5. Each carries one score.

Question 1.

The branch of Physics, that was developed to understand and improve the working of heat engines is …………

a. Optics

b. Thermodynamics

c. Electronics

d. Electrodynamics

Question 2.

State the theorem of parallel axes on a moment of inertia.

Question 3.

Select a TRUE statement from the following:

a. A year and light year have the same dimensions.

b. The intensity of the gravitational field has the same dimensions as that of acceleration.

c. One angstrom is the mean distance between sun and earth.

d. Parsec is a unit of time.

Question 4.

If the zero of potential energy is at infinity, the total energy of an orbiting satellite is negative of its …………….. energy.

Question 5.

What is the time period of a second’s pendulum?

Answer any five questions from question numbers 6 to 11. Each carries two scores.

Question 6.

Using a suitable velocity-time graph, derive the relation x = v_{0}t+ ½ at^{2}.

Question 7.

A boy throws a ball of mass 200 g with a velocity 20 ms^{-1} at an angle of 40° with the horizontal. What is the kinetic energy of the ball at the highest point of the trajectory?

Question 8.

Write the work done in each of the following cases as zero, positive or negative.

a. Work was done by centripetal force in circular motion.

b. Work was done by friction.

c. Work was done by the gravitational force on a freely falling object.

d. Work was done by the applied force in lifting an object.

Question 9.

Derive an It escapes velocity of an object from the surface of a planet.

Question 10.

A typical stress-strain graph of a metallic wire is shown below.

a. Write the name of the point B labeled in the graph.

b. For materials like copper, the points D and E are ………………. (close/far apart).

Question 11.

The terminal velocity of a copper ball of radius 2.0 mm falling through a tank of oil at 20°C is 6.5 cm s^{-1}. Calculate the viscosity of the oil at 20°C.

(Hints: Density of oil is 1.5 × 10^{3} kg m^{-3}, a density of copper is 8.9 × 10^{3 }kg m^{-3}.)

Answer any live questions from question numbers 12 to 17. Each carries three scores.

Question 12.

A body falling under the effect of gravity is said to be in free fall.

a. Draw the velocity-time graph for a freely falling object.

b. Define uniform acceleration.

c. From the given figures, identify the figure which represents uniformly accelerated motion.

Question 13.

A gun moves backward when a shot is fired from it.

a. Choose the correct statement.

i. The momentum of the gun is greater than that of the shot.

ii. The momentum acquired by Jche gun and shot have the same magnitude.

iii. Gun and shot acquire the same amount of kinetic energy.

b. A shell of mass 0.020 kg is fired by a gun of mass 100 kg. If the muzzle speed of the shell is 80 m/s, what is the recoil speed of the gun?

Question 14.

Acceleration due to gravity decreases with depth.

a. Prove the above statement by deriving the proper equation.

b. Using the equation, show that acceleration due to gravity is maximum at the surface and zero at the center of the earth.

Question 15.

A device used to lift automobiles is shown in the figure.

a. Write the name of the device

b. In the situation shown in the figure, a mass of the car is 3000 kg and area of the piston carrying it is 425cm2. What pressure is to be applied to the smaller piston?

Question 16.

Based on the kinetic theory of gases, derive an expression for the pressure exerted by an ideal gas.

Question 17.

When 0.15 kg of ice at 0°C is mixed with 0.30 kg of water at 50°C in a container, the resulting temperature is 6.7°C. Calculate the latent heat of fusion of ice. Given specific heat capacity of water 4186 J kg^{-1}K^{-1}.

Answer any four questions from question numbers 18 to 22. Each carries four scores.

Question 18.

The accuracy in measurement depends on the limit or the resolution of the measuring instrument.

a. State whether the above statement is TRUE or FALSE.

b. A physical quantity P is related to four observables a,b,c, and d as P= The percentage errors in measurements of a,b,c, and d are 1%, 3%, 2%, and 3% respectively. What is the percentage error in the measurement of P?

Question 19.

A stone tied to the end of a string 80 cm long is whirled in a horizontal circle with a constant speed.

a. What is the angle between velocity and acceleration at any instant of motion?

b. If the stone makes 14 revolutions in 25 s,

what is the magnitude of the acceleration of the stone?

Question 20.

a. If \(\xrightarrow { A }\) is perpendicular to \(\xrightarrow { B }\), what is the

value of \(\xrightarrow { A }\).\(\xrightarrow { B }\)?

b. Find the angle between the force \(\xrightarrow { F }\) = (\(3\hat { i }\) + \(4\hat { j }\) –\(5\hat { k }\))N and displacement \(\xrightarrow { d }\) = (\(5\hat { i }\) + \(4\hat { j }\) + \(3\hat { k }\))m.

Question 21.

Schematic diagram of a device is shown below.

a. Write the equation for the efficiency of the device.

b. Write the name of the four processes in the working cycle of the device

c. If T_{1} =100°C, T_{2 }= 0°C, and Q_{1} = 4200 J find the value of Q_{2
}

Question 22.

a. Which one of the following relationships between the acceleration (a) and the displacement (x) of a particle involves simple harmonic motion?

i. a = 0.7 x

ii. a = 200 x

iii. a = 10x

iv. a=100x

b. A simple harmonic motion is represented as x = A cost. Obtain the expression for velocity and acceleration of the object and hence prove that acceleration is directly proportional to the displacement.

Answer any three questions from question numbers 23 to 26. Each carries five scores.

Question 23.

a. What is the condition for the equilibrium of concurrent forces?

b. A mass of 6 kg is suspended by a rope of length 2m from the ceiling. A force of 50 N in the horizontal direction is applied at the midpoint P of the rope, as shown. What is the angle, the rope makes with the vertical in equilibrium? (Take g=10 ms 2). Neglect the mass of the rope.

c. What will be the angle made by the rope with the vertical if its length is doubled?

Question 24.

a. Write the equation connecting torque with force.

b. A meter stick is balanced at its cecenter50 cm). When two coins, each of mass 5 g, are put one on the top of the other at the 12 cm mark, it is found to be balanced at 45 cm. What is the mass of the stick?

c. Derive the relation connecting torque with angular momentum.

Question 25.

a. Water rises up in a narrow tube in spite of gravity. This phenomenon is called…

b. Derive an expression for the height of water in the tube in terms of the radius of the tube and surface tension of the liquid.

c. Water with detergent dissolved in it should have an angle of contact. (Small/large)

Question 26.

The fundamental mode of vibration of a stretched string is shown below.

a. Draw the second and third harmonics.

b. Prove that frequencies produced in the string are in the ratio of 1: 2: 3.

c. Let the fundamental frequency is 45 Hz and the length of the wire is 87.5 cm. If the linear density of the wire is 4.0 × 10^{2} kg/m. Find the tension in the string

Answers

Answer 1.

Thermodynamics

Answer 2.

This theorem is good for any shape. The moment of inertia of the body about any axis is equal to the sum of a moment of inertia of a parallel axis passing through the center of mass and product of its mass of the body and square of the distance between the two parallel axes. I = I_{g} + Ma^{2}

Answer 3.

b

Answer 4.

Kinetic energy

Answer 5.

T = 2sec

Answer 6.

The area under the velocity-time graph gives the displacement of the body. Displacement, x = area OABD x = area of triangle ABC+ area of rectal

Answer 7.

At the top V = 0, V_{x} = ucosθ

Answer 8.

a. Zero

b. Zero or negative ( 0 for static)

c. Positive

d. Positive

Answer 9.

The total work done to move a body of mass’m’ from the surface of the earth (r=R) to

infinity (r = ) is given by, \(W=\frac { GMm }{ R }\)

Let v be the velocity of the body, then K.E of the body, when projected, is K = 1/2 mv^{2} The body can escape from the gravitational pull of earth only if the KE is greater than or equal to the work done in overcoming the gravity.

Answer 10.

a. Elastic limit or Yield point

b. Far apart (Copper is malleable)

Answer 11.

Answer 12.

b. Equal change in velocity in an equal time interval.

c. Fig(3)

Answer 13.

Answer 14.

Answer 15.

a. Hydraulic Lift

Answer 16.

Consider a gas contained in a cubical vessel of side 7 and volume V = B. Let there be ‘n’ molecules per unit volume of the gas, each of masses’. Hence the total mass of the gas in the vessel M = nm × v The molecules are having random velocities and since the motion is not under a force. Consider such a molecule moving with a velocity V along X-direction as shown in the figure. As it moves in the positive X-direction it undergoes elastic collision and is a bounce from the wall O’A’B’C’. The momentum of the molecule before collision = mv

Momentum after collision=mv (rebounding) Change in momentum= mv (mv) = 2mv Hence the change of momentum imparted to the wall = 2mv For this molecule to undergo the next collision with the same wall it has to travel a distance 2l. The time to travel this distance by the molecule is given by t = 2//v Number of collision per second with this wall =\(\frac { l }{ t }\) = \(\frac { l }{ 2l }\)

According to Newton’s second law change in momentum per second = force on the wall. i.e., the thrust by 1 molecule. Taking all the ‘n’ molecules in a unit volume of the vessel, each will be travelling in x, y, z direction on the average. Let V_{1} V_{2}, V_{3}, ………… V_{n} be the velocities of n molecules. Then average value of velocity square is shown as below.

where \(\vec { V }\) is called the root mean square velocity (rms velocity of the molecule), rms velocity of a gas molecule is defined as the square root of the mean of the squares of the velocities of the gas molecules. It is given by

Answer 17.

Answer 18.

Answer 19.

Answer 20.

Answer 21.

b. Isothermal expansion Adiabatic expansion Isothermal compression Adiabatic compression

Answer 22.

Answer 23.

a. Vector sum of all the forces = 0

c. All the fores are independent of length (for massless string)

Answer 24.

Differentiating with respect to line

Answer 25.

a. Cappilarity/Capillary rise

b. 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 rdip ped 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 heightLet ‘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 liquid outside.

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

c. Small

Answer 26.

In an open tube, both ends are open. At both ends, antinodes are formed. The mode of vibration of the open organ pipe are