Physics national exam 2013 – SMART ETHIO E-Learning

Welcome to your Physics national exam 2013

CHOOSE

1.

The second law of thermodynamics states that

two bodies that are separately in thermal equilibrium with a third body must be in thermal equilibrium with each other.

no process is possible in which there is an overall increase in the entropy of the universe.

no process is possible in which there is an overall decrease in the entropy of the universe.

the increase in the internal energy of a system is equal to the sum of the energy entering the system through heating, and work done on the system.

2.

A mass-spring system set to oscillate in a simple harmonic motion over friction less horizontal surface. The amplitude of this oscillation is 20 cm. A second ass-spring system with the same spring constant is set to oscillate in the same way but with amplitude of 10 cm. The energy of the

second mass-spring system has the square of the first one.

first mass-spring system has twice the second one.

second mass-spring system has half of the first one

first mass-spring system has four times the second one.

3.

Suppose you are given the following travelling waves that have the same frequency and the same amplitude A.

Amplitude(cm)

Amplitude(cm)

Which graph represents the supper of the two waves?

(second)

Amplitude(cm)

Amplitude(cm)

Amplitude(cm)

4.

A string vibrates with speed of 110 m/s in its fourth harmonic has a frequency of 880 Hz. What is the length of the string?

31.3 cm

50.0 cm

12.5 cm

25.0 cm

5.

An interference patterns observed after a monochromatic beam of light passes through a single slit and a double slit. Which one of the following is correct about the width of the central maxima and the first order maxima in single slit and double slit?

The width of the central maxima and first order maxima has equal width in both cases.

The width of the central maxima has equal with the width of the first order maxima in a single slit interference while it has twice the width of the order maxima in double slit interference.

The width of the central maxima has twice the width of the first order maxima in both cases.

The width of the central maxima has twice the width of the first order maxima in a single slit interference while it has equal width in double slit interference.

6.

A light wave of wavelength 590 nm pass through a narrow double slit of 0.2 mm slit separation. An interference pattern is formed on a screen at a distance of 1.5 m. What is the distance between the consecutive bright fringes on the screen?

1.97 mm

4.43mm

44.3 mm

0.43 mm

7.

According to Gauss's law the net electric flux through any hypothetical closed surface is proportional to the enclosed;

Electric charge.

Electric current.

Electric field.

Potential difference.

8.

When a dielectric material placed between two parallel metal plates in the presence of electric fields they enable the plates to store

much more charge at the same potential difference.

the same charge at the same potential difference.

much more charge at different potential difference.

much less charge at difference potential difference.

9.

A parallel plate capacitor with plate area A and plates separation stores a charge Q when a potential difference V is kept between the plates. Then the region between the plates is completely filled with a dielectric material of dielectric constant e r . If E denotes the electric field between the plates, the energy density stored by the capacitor is

10.

A uniform conductor of length L and cross-sectional area A carries a current Z when a potential difference V is applied across its ends. If the number free electrons per unit volume of the conductor in n and the electron charge is e, then the drift velocity of the electrons in the conductor is

11.

which one of the following statement is correct about, a Bar on which a force acts at one end and pivoted at the other ?

The force, angular velocity and the torque are complainer

The force is coplanar with the torque it produces

The force is collinear with the angular velocity

The force is parallel to the angular acceleration produced

12.

The necessary condition for an object to be in rotational equilibrium is

the net moment of all forces should be non-zero.

the net force exerting on the object must be zero.

the sum of clockwise torques equals to the sum of counter clock. wise torques.

the net torque action on the object is different from zero.

13.

An aluminum wire of initial length 2.0 m where increased by 2.0 cm in its length Being on application of a force of 9.0 N. What is the strain energy of the material?

4.5x 10 ‾ 2 J

0. 9 J

9.0 x 10 2‾ 2 J

0.18 J

14.

Ethanol has a surface tension of 22 x 10 -³ N/m and its density is of 789 g/cm³. The radius of the capillary tube is 15 mm, and the contact angle is 30⁰ . Determine the height rise in the column of the capillary tube.

3.2 mm

0.16 mm

1.6 mm

0.32 mm

15.

Suppose a stream of fluid flows past a solid object, which one of the following does NOT affect the linear flow of the fluid?

The speed of the solid object

The density of the solid object

viscosity of the fluid

The shape of the solid object

16.

Water enters a tube of non-uniform The speed of the force at the entry of area A
₁ is 12 m/s and the speed becomes 4 m/s at the exit opening of area A₂ . Which one is correct
about the ratio of

1/4

1/3

4

3

17.

The particular temperature and pressure at which the solid, liquid, an gaseous phases of a given substance are all at equilibrium with another is known as:

Heat capacity.

Triple point.

Phase change.

Critical point.

18.

Most solids expand upon heating, which one of the following statements correctly describe the phenomena?

Increase in temperature decreases the vibrational kinetic energy and amplitude of the atoms constituting the solid.

Increase in temperature increases the vibrational kinetic energy and decreases the amplitude of the atoms constituting the solid.

Increase in temperature increases the vibrational kinetic energy and amplitude of the atoms constituting the solid.

Increase in temperature decreases the vibrational kinetic energy and increases the amplitude of the atoms constituting the solid.

19.

If 25 J is taken away by heat from a system, and the system does 20 J of work, what is the change in internal energy of the system?

5.0 J

-45.0 J

-5.0 J

45.0 J

20.

A sample mixture of gas contains 72% of hydrogen Answer: C um. What is the partial pressure of helium at an ot 28% of Helios 76 cm of mercury (Hg) ?

21.28 cm of Hg

76.0 cm of Hg

33.44 cm of Hg

54.72 cm of Hg

21.

Kirchhoff s junction rule state that

the potential drop at a given junction equals the electromotive force at that particular point.

charge entering the junction equals the charge leaving that junction at a particular time.

current traversing any closed loop at particular time is zero.

the same of the voltage drop across any closed loop equals the sum of electromotive force.

22.

Which one of the following statement is NOT correct about the magnetic properties of matter?

The unpaired electrons in paramagnetic substance which will tend to align themselves in the same direction as the applied magnetic field.

There is a tendency to oppose the applied magnetic field in a diamagnetic substance.

The unpaired electrons in ferromagnetic materials will align with the applied magnetic field and parallel to each other.

The unpaired electrons in diamagnetic materials will align with the applied magnetic field and parallel to each other.

23.

suppose a conductor of length 1 carrying a current I placed in a uniform magnetic field of magnitude B. When the conductor is making an angle Θ with that of the magnetic field then force experienced by the conductor due to the magnetic field is given by

24.

Which on of the following statement is correct about tangent galvanometer?

It is a device used to measure the electric current in terms of the electric field it produces.

It consists of a coil of insulated copper wire on a circular magnetic frame.

The current through a coil of the wire generates a magnetic field at the center of COC.

The current is inversely proportional to the tangent of the angle of the needle's deflection.

25.

A long conductor shown in the figure carries a current I in the direction indicated by the arrow. Which statement is NOT correct about the magnetic field produced by this current carrying conductor?

The field strength is directly proportional to the distance from the conductor.

Reversing the current direction will reverse the direction of the magnetic field.

The magnetic field encircles conductor.

Doubling the current through the conductor doubles the field strength.

26.

A coiled copper has 50 turns and coil Cross-sectional area of 9 x 10.m2. This coil is Initially placed m a uniform magnetic field 0.02 T and pulled out of a field completely (where the field is zero) in 0.5 seconds, What is the magnitude of the induced electromotive force?

9.0mV

18mV

3.2 mV

1.8mV

27.

A 15.0mH inductor is used to induce an electromotive force of 5.0 in V. What is the rate change of the induced current?

3.3 A/s

0.33 A/s

3.0A/s

0.30 A/s

28.

A coil and a permanent magnet are set in relative motion. Which one of the following statement is NOT correct about induced electromotive force?

The magnitude of the induced electromotive force is directly proportional to the relative velocity between the two.

Moving a magnet relative to the coil and the coil relative to the magnet with equal speed will produce the same electromotive force.

Coil with larger number of turns produce greater induced electromotive forces.

The direction in which the coil moves relative to the magnetic field does not have any effect on the induced electromotive force.

29.

what is the advantage of using alternating current in transmission of electric energy.

It enables to reach the consumers at very high voltage.

it uses very high current in the transmission line.

It enables a transformer to increase or decrease the voltage as required.

It completely avoids energy loss due to heating.

30.

Capacitive reactance is defined as

The equivalent quantity to impedance in RLC cineuit.

The equivalent quantity to resistance when we are talking about capacitors.

The equivalent quantity to resistance when we are talking about resistors.

The equivalent quantity to resistance when we are talking about inductors.

31.

Which one of the following is NOT connect about the concept and units of coefficient or friction?

Coefficient of friction is the ratio of frictional force to normal force.

The coefficient of friction is always less or equal to unity (1).

Coefficient of static friction has no unit.

Coefficient of static friction is less than its value of kinetic friction.

32.

A car is travelling at constant velocity along a straight line. Which, statement is correct?

The net force on the car is different from zero.

The displacement of the car is in opposite direction.

The displacement of the car increase linearly with time.

The acceleration of the car is m opposite direction.

33.

Which one of the following statements is correct about the impulse on an object?

Impulse is the change in momentum when a force is exerted on an object for a very short period of time.

The area under the curve of momentum versus time graph is the impulse on an object.

the impulse on an object is changed when the net force acting on the object is zero.

Impulse is the rate of change in momentum due to external force exerted on an object for a very short period of time.

34.

Consider two collisions, that occurred between two trollies having the same mass; moving the same speed, and in opposite directions,

Collision 1:- after collision the two trollies
bounce back with the same speed.

Collision 2:- after collision the two trollies
back with the same coupler

Both collisions are elastic.

Both collisions are Inelastic.

Collision 1 is elastic and collision 2 is inelastic.

Collision 1 is inelastic is inelastic and collision 2 elastic.

35.

Suppose that you are given a mass attached to a spring and oscillates up and down. This mass-spring system has maximum gravitational potential energy (GPE), elastic potential energy (EPE) and kinetic energy (KE) at the

bottom, middle and top respectively.

top, bottom and middle respectively.

middle, bottom and top respectively.

middle, top and bottom respectively.

36.

A pendulum shown in the figure below

has 2.5 m length and mass
m . When It passes point A, its
mass has a speed of 2.0 m/s.
(neglect the air resistance)

The height of the pendulum at displacement

position B and c is

0.4m

0.1 m

2.5m

0.2 m

37.

A 5.0 kg stone is dropped from a top of 30.0 m building. At a height of 10.0 m above the ground, 60% of its initial potential energy is converted to kinetic energy. Which one of the following statements is correct about the transformation of energy for the stone ?

6.7 % of its gravitational potential energy is dissipated due to air resistance.

The remaining 408 of the energy is still available as gravitational potential energy

The sum of its potential energy and kinetic energy is the same at every point during its fall.

80 of its original potential energy is converted to heat energy dues to air resistance.

38.

A glass contains 12 mole of water molecule (HCO). The number of water molecules, the mass of water, and the mass of each molecule in the glass are, respectively (Molar mass of II is 1 0 8 and O is t6.0 a )

39.

A wheel starts rotating at 1.2 Hz and reaches 1.8 Hz in S seconds. Calculate the angular displacement it covers within S seconds.

3 πrad

30 πrad

15 πrad

10 πrad

40.

Ratio of linear momentum to moment of Inertia.

product of moment of inertia and angular speed.

ratio of moment of inertia to angular acceleration.

product of moment of inertia and torque.

41.

A student wants to measure the length and height of the school laboratory. There are Vernier calipers, meter stick, micrometer screw gauge and meter tape measuring instruments in the laboratory. Which one of the following measuring instruments and unit is appropriate for the measurement ?

Meter tape and meter

Meter stick and centimeter

Vernier calipers and millimeter

Micrometer screw gauge and millimeter

42.

In reporting an experimental result the collected data has to be clearly tabulated with appropriate units. which of the following table correctly represents a data collected during an experiments?

43.

A 10 N force is applied in the direction of North-east, which of the following graphical representational of the force is correct? (Assume the lengths of all arrows are equal and the paper head points towards North)

44.

Two vectors of magnitude 8 unit in the direction of East and the second vector of magnitude S units in the direction of North are given. If you add the two vectors using graphical method, which graph represents the resultant of the vectors?

45.

Which of the following pair of vectors are collinear

46.

Instantaneous velocity is different from average velocity in that; instantaneous velocity is

the velocity at a particular instant of time.

in opposite direction to the displacement of the moving object.

the average velocity during the time of acceleration.

the total displacement to the fine taken.

47.

A car travelling at 20 m/s starts to speedup. After 5 minutes its speed is 144 m/s. What is the acceleration of the car?

24.8 m/s

28.8 m/s

0.41 m/s

0.55 m/s

48.

A bullet of 200 g mass fired from a 30.0 m high building, horizontally. At the same time a bullet of the same mass fired vertically down from the same height. What can be concluded about the motion of the two bullets?

A bullet fired vertically takes more time to strike the ground.

Both bullets strike the ground at the same time.

A bullet fired horizontally takes more time to strike the ground.

Both bullets move with the same horizontal velocity.

49.

A bird flies at speed of 10 m/s south relative to the Earth. A wind blows at speed of 4 m/s to east relative to the Earth. What is the speed of the bird relative to the wind?

8 m/s in the direction of South-East

10.8 m/s in the direction of North-West

10.8 m/s in the direction of South-West

8 m/s m the direction of North-East

50.

Dynamics is a branch of mechanics concerned with the motion of an object

whose velocity is constant.

under the cation of balanced forces.

without its causes.

under the cation of forces.

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