Physics · NDA previous year questions

Two long wires each carrying a d.c. current in the same direction are placed close to each other. Which one of the following statements is correct?

1. A.The wires will attract each other
2. B.The wires will repel each other
3. C.There will be no force between the wires
4. D.There will be a force between the wires only at the moment when the current is switched ON or OFF

The absolute zero, i.e., temperature below which is not achievable, is about:

1. A.$0{}^{\circ }\mathrm{C}$
2. B.$-273\mathrm{K}$
3. C.$-273{}^{\circ }\mathrm{C}$
4. D.$-300{}^{\circ }\mathrm{C}$

Lightning conductors are used to protect building from lightning strikes. Which of the following statements is / are true about lightning conductors? 1. Lightning conductors create an electric field at its top so that lightning strikes it preferentially 2. Lightning conductors reduce the effect of the strike by uniformly distributing the charge (current) over the surface of the building 3. Lightning conductors take all charge (current) to deep down in the earth 4. Lightning conductors must be installed at a place taller than the building Select the correct answer using the code given below:

1. A.1 and 2
2. B.3 and 4 only
3. C.1, 3 and 4
4. D.4 only

The silvering in thermos flasks is done to avoid heat transfer by:

1. A.Convection
2. B.Conduction
3. C.Radiation
4. D.Both convection and conduction

Conservation of momentum in a collision between particles can be understood on the basis of:

1. A.Newton’s first law of motion
2. B.Newton’s second law of motion only
3. C.Both Newton’s second law of motion and Newton’s third law of motion
4. D.Conservation of energy

Two forces, one of 3 newton and another of 4 newton are applied on a standard 1 kg body, placed on a horizontal and frictionless surface, simultaneously along the x-axis and the y-axis, respectively, as shown below: The magnitude of the resultant acceleration is:

1. A.$7m/{\mathrm{s}}^2$
2. B.$1m/{\mathrm{s}}^2$
3. C.$5m/{\mathrm{s}}^2$
4. D.$\sqrt{7}m/{\mathrm{s}}^2$

Magnetic meridian is an imaginary:

1. A.line along north-south
2. B.point
3. C.vertical plane
4. D.horizontal plane

In SI unit of force ‘Newton’ (N) is given by (where m stands for metre and s stands for second):

1. A.$1\mathrm{N}=1kg/m{\mathrm{s}}^2$
2. B.$1\mathrm{N}=1kgm/{\mathrm{s}}^2$
3. C.$1\mathrm{N}=1\mathrm{kg}{\mathrm{s}}^2/m$
4. D.$1\mathrm{N}=1\mathrm{kg}\mathrm{m}{\mathrm{s}}^2$

The acceleration due to gravity ‘g’ for objects on or near the surface of earth is related to the universal gravitational constant ‘G’ as (‘M’ is the mass of the earth and ‘R’ is its radius):

1. A.$G=g\frac{M}{R^2}$
2. B.$g=G\frac{M}{R^2}$
3. C.$M=\frac{gG}{R^2}$
4. D.$R=\frac{gG}{M^2}$

The loudness of sound is related to:

1. A.its frequency
2. B.its amplitude
3. C.its speed
4. D.its pitch

X-rays are electromagnetic radiation whose wavelengths are of the order of:

1. A.1 metre
2. B.$10^{-1}$ metre
3. C.$10^{-5}$ metre
4. D.$10^{-10}$ metre

Which one of the following statements is not correct?

1. A.The radius of curvature of a concave mirror is twice its focal length
2. B.Power of a convex lens is negative and that of a concave lens is positive
3. C.The radius of curvature of a plane mirror is infinity
4. D.When a ray of light passes from an optically denser medium to an optically rarer medium, the angle of refraction is greater than the corresponding angle of incidence

Which one of the following statements is not correct?

1. A.If the velocity and acceleration have opposite sign, the object is slowing down
2. B.If the velocity is zero at an instant, the acceleration should also be zero at that instant
3. C.If the velocity is zero for a time interval; the acceleration is zero at any instant within the time interval
4. D.If the position and velocity have opposite sign, the object is moving towards the origin

Three equal resistances when combined in series are equivalent to 90 ohm. Their equivalent resistance when combined in parallel will be:

1. A.10 ohm
2. B.30 ohm
3. C.270 ohm
4. D.810 ohm

The following figure represents the velocity-time graph of a moving car on a road: Which segment of the graph represents the retardation?

1. A.AB
2. B.BC
3. C.CD
4. D.None

Which one of the following statements is not correct?

1. A.The Kelvin scale of temperature is called the Absolute scale
2. B.Visible light radiation has wavelength range of 400—700 nm
3. C.The capacity to do work is called power
4. D.The wavelength of Gamma rays is less than that of X-rays

A man is sitting in a train which is moving with a velocity of 60 km/hour. His speed with respect to the train is:

1. A.10/3 m/s
2. B.60 m/s
3. C.infinite
4. D.zero

The resistance of a wire of length l and area of cross-section a is x ohm. If the wire is stretched to double its length, its resistance would become:

1. A.2 x ohm
2. B.0.5 x ohm
3. C.4 x ohm
4. D.6 x ohm

Addition of gypsum to cement:

1. A.reduces setting time of cement
2. B.produces very light colour cement
3. C.increases setting time of cement
4. D.shining surface is formed

White Phosphorus glows in the dark due to:

1. A.amorphous character
2. B.slow oxidation
3. C.high ignition temperature
4. D.good conducting property of electricity

Light waves are

1. A.electro-mechanical waves
2. B.electro-magnetic waves
3. C.electro-optical waves
4. D.magneto-optical waves

A particle is moving in a circular path of radius r at a constant speed v. Which one of the following graphs correctly represents its acceleration a?

1. A.Option A
2. B.Option B
3. C.Option C
4. D.Option D

Fahrenheit and Celsius are the two scales used for measuring temperature. If the numerical value of a temperature recorded in both the scales is found to be same, what is the temperature?

1. A.- 40°
2. B.+ 40°
3. C.+ 72°
4. D.- 72°

Which one of the following processes explains the splitting of a beam of white light into its constituent colours?

1. A.Dispersion
2. B.Reflection
3. C.Diffraction
4. D.Polarization

Two bodies A and B having masses m and 4m respectively are moving with equal linear momentum. The ratio of kinetic energies between A and B is

1. A.1 : 4
2. B.4 : 1
3. C.1 : 1
4. D.1 : 2