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A charged spherical conductor has potential of 6V and its radius is 2m. The electric intensity at its centre is :

a) zero b) 3 N/C c) 12 N/C d) none of the above Answer: a) zero Solution: Electric intensity inside a charged sphere is zero,... View Article

A 10g bullet is fired at a plank of wood with a speed of 200ms⁻¹. After passing through the plank, which is 1m thick, the speed of the bullet reduces to 100ms⁻¹. Find the average resistance offered by the plank.

Answer: 150 N Solution: Using v2=u2 −2as and putting v=100m/s, u=200m/s and s=1m we get retardation a=1.5×104 m/s2 so average resistance... View Article

A pendulum clock that keeps the correct time on the earth is taken to the moon. It will run

a) at correct rate b) 6 times faster c) √6 times faster d) √6 times slower Answer: d) √6 times... View Article

A train covers a distance of 270 km at a uniform speed. Had the speed been 15 km/hour more, it would have taken one and a half hours to cover the same distance. Find the original speed of the train.

Answer: 45 km/hr Solution: Original speed of train = 90/x km/hr Increased speed of train 90/(x+15) km/hr Given, (90/x) - (90/x+15) =... View Article

The rays of different colours fail to converge at a point after going through a converging lens. This defect is called :

(a) spherical aberration (b) distortion (c) coma (d) chromatic aberration Answer: (d) chromatic aberration Since the refractive index... View Article

The angular frequency of a simple pendulum is ω rad/sec. Now, if the length is made one-fourth of the original length, the angular frequency becomes

a) ω/2 b) 2ω c) 4ω d) ω Answer: b) 2ω Solution: ω = 2πv = 2π x (1/2π)... View Article

A thin wire loop carrying a current I is placed in a uniform magnetic field B pointing out of the plane of the coil as shown in the figure. The loop will tend to

a) moves towards positive x-direction b) moves towards negative x direction c) expand d) contract Answer: c) expand Solution: The net force... View Article

A bullet of mass 0.04 kg moving with a speed of 90m/s enters a heavy wooden block and is stopped after a distance of 60 cm. What is the average force exerted by the block on the bullet?

Answer: - 270 N Solution: From 3rd equation of motion 2as = v2 - u2 a = -u2/2s = - (90 x 90)/(2 x 60 x 10-2) = - 6750 m/s2... View Article

A body of mass 10 mg is moving with a velocity of 100 ms^-1. The wavelength of the de-Broglie wave associated with it would be (Note: h = 6.63 × 10^-34 Js)

Answer: 6.626 x 10-31 m Solution: de Broglie wavelength λ = h/mv = (6.626 x 10-34 ) / (10 x 10-6 x 100) = 6.626 x... View Article

A 1000 kg rocket is fired from the surface of the earth so that its exhaust speed is 1000 m/s relative to the rocket. If the initial acceleration of the rocket is 5m/s² then the mass of fuel-burning per second is
(Take, g=10m/s²)

a) 15 kg/s b) 5 kg/s c) 10 kg/s d) 20 kg/s Answer: a) 15 kg/s Solution: M (g + a) = V. (dm/dt) M is the initial mass g is... View Article

Two capacitors when connected in series have a capacitance of 3μF, and when connected in parallel have a capacitance of 16μF. Their individual capacities are :

a) 1μF, 2 μF b) 6 μF, 2 μF c) 12 μF, 4 μF d) 3 μF, 6 μF Answer: c) 12 μF, 4 μF... View Article

A wheel rotates with the constant acceleration of 2.0 rad/s², if the wheel starts from rest the number of revolutions it makes in the first ten seconds will be approximately

a) 32 b) 24 c) 16 d) 8 Answer: c) 16 Solution: If θ be the angular displacement, then θ=(1/2)αt2... View Article

The work done by a body on application of a constant force is directly proportional to the distance traveled by the body. Express this in the form of an equation in two variables and draw the graph of the same by taking the constant force as 5 units. Read from the graph, the work done when the distance traveled by the body is 0 units

a) 0 units b) 2 units c) 1 units d) 3 units Answer: a) 0 units Solution: Consider work done =y units when the distance travelled =x units.... View Article

What is the magnitude of the equatorial and axial fields due to a bar magnet of length 5.0 cm at a distance of 50cm from its mid-point? The magnetic moment of the bar magnet is 0.40 Am²

Answer: 3.2 x 10-7 T and 6.4 x 10-7 N Solution: Bequatorial = μ0m/4πr3 = (10-7 x 0.4)/(0.5)3 = 3.2 x 10-7 N... View Article

Two waves in the same medium are represented by y-t curves in the figure shown. Find the ratio of their average intensities?

a) 25/16 b) 23/16 c) 21/16 d) 27/16 Answer: a) 25/16 Solution: I ∝ A2ω2 (I1/I2) = A12ω12/A22ω22 = (f12 x A12)/(f22 x A22) = (1 x 25)/(4... View Article

A continuous conveyor belt passes over two discs A and B of radii R and 4R respectively. They start
from rest. A has an angular acceleration of (π/4)rad s^-2. What is the angular velocity of disc B at the end
of 32 sec?

a) π rad /s b) 2π rad /s c) 4π rad /s d) π/4 rad /s Answer: b) 2π rad /s Solution: First, find the angular velocity of the belt at disc A... View Article

A prism of apex angle A=60⁰ has the refractive index μ=√2. The angle of incidence for minimum deviation is

A) 300 B) 450 C) 600 D) None of these Answer: B) 450 Solution: For minimum deviation, r1=r2=A/2=300 Now using,... View Article

In a particular system the units of length, mass and time are chosen to be 10 cm, 10 g and 0.1 s respectively. The unit of force in this system will be equal to

a) 0.1 N b) 1 N c) 10 N d) 100 N Answer: a) 0.1 N Solution: Given, length x = 10 cm mass m = 10 g time t = 0.1 sec We know... View Article

When photons of energy 4.25 eV strike the surface of a metal A, the ejected photoelectrons have a maximum kinetic energy of T_A eV and de Broglie wavelength λ_A. The maximum kinetic energy of photoelectrons liberated from another metal B by photons of energy 4.70eV is T_B=(T_A−1.5)eV. If the de Broglie wavelength of these photoelectrons is λ_B=2λ_A then

a) the work function of A is 2.25 eV b) the work function of B is 4.20 eV c) KA = 2.00 eV d) KB = 2.75 eV Answer: a, b, c... View Article

Action and reaction forces

i. Act on the same body ii. Act on different bodies iii. Act in same direction iv. Both i and iii Answer: ii. Act on different... View Article