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A person standing on a spring balance inside a stationary lift measures 60 kg. The weight of that person if the lift descends with uniform downward acceleration of 1.8 m/s²will be ___________ N. [g =10m/s²]

Answer: 492 Mg – N = Ma N = M(g–a) N = 60(10–1.8) N = 60 × 8.2 = 492 N... View Article

The maximum and minimum amplitude of an amplitude-modulated wave is 16 V and 8 V respectively. The modulation index for this amplitude modulated wave is x ×10^–2. The value of x is ________

Answer: 33 Am = (Amax- Amin)/2 AC = (Amax+ Amin)/2 Modulation index (mi) =Am/AC = (Amax - Amin)/2/(Amax + Amin)/2 = (Amax- Amin)/(Amax+ Amin) mi... View Article

A boy pushes a box of mass 2 kg with a force [latex]vec{F}=(20hat{i}+10hat{j})N[/latex] on a frictionless surface. If the box was initially at rest, then __________m is displacement along the x-axis after 10 s.

Answer: 500 Fx = 20 N Fy = 10 N ax = Fx/M = 20/2 = 10 m/s2 Displacement on x-axis is Sx = uxt + ½ axt2 Sx = 0 × 10 +... View Article

A container is divided into two chambers by a partition. The volume of the first chamber is 4.5 litre and the second chamber is 5.5 litre.

A container is divided into two chambers by a partition. The volume of the first chamber is 4.5 litre and the second chamber is 5.5 litre. The... View Article

In an electrical circuit, a battery is connected to pass 20 C of charge through it in a certain given time. The potential difference between two plates of the battery is maintained at 15 V. The work done by the battery is __________ J.

Answer: 300 Charge flown (Q) = 20 C Potential difference (V) = 15 V Work done (w) = Q.V ⇒ 20 × 15 = 300 J... View Article

In a series LCR resonant circuit, the quality factor is measured as 100. If the inductance is increased by two fold and resistance is decreased by two fold, then the quality factor after this change will be __________. (up to two decimal places).

Answer: 282.84 Quality factor = XL/R = ωL/R Q = (1/√(LC)) (L/R) Q = (1/√C)(√L/R Q' = √(2L)/(R/2)√C =... View Article

As shown in the figure, a block of mass √3 kg is kept on a horizontal rough surface of coefficient of friction 1/3√3.

As shown in the figure, a block of mass √3 kg is kept on a horizontal rough surface of coefficient of friction 1/3√3. The critical... View Article

The circuit contains two diodes each with a forward resistance

The circuit contains two diodes each with a forward resistance of 50 Ω and with infinite reverse resistance. If the battery voltage is 6 V,... View Article

A radiation is emitted by a 1000 W bulb, and it generates an electric field and magnetic field at P, placed at a distance of 2 m.

A radiation is emitted by a 1000 W bulb, and it generates an electric field and magnetic field at P, placed at a distance of 2 m. The efficiency... View Article

The mass per unit length of a uniform wire is 0.135 g/cm.

The mass per unit length of a uniform wire is 0.135 g/cm. A transverse wave of the form y = –0.21sin(x+30t) is produced in it, where x is... View Article

In a typical combustion engine the work done by a gas molecule is given by [latex]W= alpha ^{2}beta e^{frac{-beta x^{2}}{kT}}[/latex] , where x is the displacement, k is the Boltzmann constant and T is the temperature. If α and β are constants, dimensions of α will be:

a. [M0 L T0] b. [M2 L T–2] c. [M L T–2] d. [M L T-1] Answer:(a) βx2/kT is dimensionless So, [kT] = [βx2]... View Article

If two similar springs each of spring constant K₁ are joined in series, the new spring constant and time period would be changed by a factor:

a. ½, √2 b. ¼, 2√2 c. ½, 2√2 d. ¼, √2 Answer: (a) Keq = K1 ×K1/(K1+K1) = K12/2K1... View Article

Consider the combination of 2 capacitors C₁ and C₂, with C₂>C₁, when connected in parallel, the equivalent capacitance is 15/4 times the equivalent capacitance of the same connected in series. Calculate the ratio of capacitors, C₂/C₁.

a.15/11 b.29/15 c.15/4 d. 111/80 Answer: Bonus C1 + C2 = (15/4)C1C2/(C1 + C2) 4 (C1 + C2)2 = 15C1C2 4C12 + 4C22 – 7C1C2 = 0 4 + 4... View Article

An alternating current is given by the equation i = i₁sinωt + i₂cosωt. The rms current will be:

a. ½ (i12 + i22)1/2 b. (1/√2) (i12 + i22)1/2 c. (1/√2) (i1 + i2)2 d. (1/√2) (i1 + i2) Answer: (b) We know that, Irms =... View Article

A planet revolving in elliptical orbit has:

A. a constant velocity of revolution. B. has the least velocity when it is nearest to the sun. C. its areal velocity is directly proportional... View Article

A large number of water drops, each of radius r, combine to have a drop of radius R. If the surface tension is T and mechanical equivalent of heat is J, the rise in heat energy per unit volume will be:

a. 2T/rJ b. 3T/rJ c. (2T/J)(1/r - 1/R) d. (3T/J)(1/r -1/R) Answer: (d) R is the radius of bigger drop. r is the radius of smaller drops. Water... View Article

A particle is moving with uniform speed along the circumference of a circle of radius R under the action of a central fictitious force F which is inversely proportional to R³. Its time period of revolution will be given by:

a. T ∝ R5/2 b. T ∝ R2 c. T ∝R4/3 d. T ∝ R3/2 Answer: (b) F∝1/R3 F = K/R3 mv2/R = K/R3 m(ωR)2 = K/R2 mω2R2 =... View Article

A short straight object of height 100 cm lies before the central axis of a spherical mirror whose focal length has absolute value |f| = 40 cm. The image of the object produced by the mirror is of height 25 cm and has the same orientation as the object. One may conclude from the information:

a. Image is real, same side of concave mirror b. Image is virtual, opposite side of convex mirror. c. Image is virtual, opposite side of... View Article

Given below are two statements: one is labelled as Assertion A and the other is labelled as Reason R.

Given below are two statements: one is labelled as Assertion A and the other is labelled as Reason R. Assertion A: Body 'P' having mass M moving... View Article

Find the electric field E at point P

Find the electric field E at point P (as shown in the figure) on the perpendicular bisector of a uniformly charged thin wire of length L carrying... View Article