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# JEE Physics 2013 Exam Questions

#### Multiple Choice Questions

1.

A hoop of radius r and mass m rotating with an angular velocity ω0
is placed on a rough horizontal surface.The initial velocity of the centre of the hoop is zero. What will be the velocity of the centre of the hoop when it ceases to slip?

• 0/4

• 0/3

• 0/2

• 0

C.

0/2

From conservation of angular momentum about any fixed point on the surface

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2.

A projectile is given an initial velocity of  where is along the ground and  is along the vertical. If g = 10 m/s2, the equation of its trajectory is:

• y = x-5x2

• y = 2x-5x2

• 4y = 2x- 5x2

• 4y = 2x-25x2

B.

y = 2x-5x2

Initial velocity,
Magnitude of velocity,

the equation of trajectory of the projectile

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3.

Let [ε0] denote the dimensional formula of the permittivity of vacuum. If M = mass, L = length, T = time and A = electric current, then

• 0] = [M-1L-3T2A]

• 0] = [M-1L-3T4A2]

• 0] =[M-2L2T-1A-2]

• 0] = [M-1L2T-1A2]

B.

0] = [M-1L-3T4A2]

From Coulomb's Law, F

On Substituting the units, we get

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4.

A uniform cylinder of length L and mass M having cross-sectional area A is suspended, with its length vertical, from a fixed point by a massless spring, such that it is half submerged in a liquid of density σ at the equilibrium position. The extension x0 of the spring when it is in equilibrium is

C.

At equilibrium ΣF = 0

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5.

A sonometer wire of length 1.5 m is made of steel. The tension in it produces an elastic strain of 1 %. What is the fundamental frequency of steel if density and elasticity of steel are 7.7 × 103 kg/m3 and 2.2 × 1011N/m2 respectively?

• 188.5 Hz

• 178.2 Hz

• 200.5 Hz

• 770 Hz

B.

178.2 Hz

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6.

The amplitude of a damped oscillator decreases to 0.9 times its original magnitude is 5s. In another 10s it will decrease to α times its original magnitude, where α equals

• 0.7

• 0.81

• 0.729

• 0.6

C.

0.729

Amplitude of damped oscillator

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7.

What is the minimum energy required to launch a satellite of mass m from the surface of a planet of mass M and radius R in a circular orbit at an altitude of 2R?

• 5GmM/6R

• 2GmM/3R

• GmM/2R

• GmM/3R

A.

5GmM/6R

From conservation of energy,
Total energy at the planet = Total energy at the altitude

In its orbit the necessary centripetal force provided by gravitational force.
∴

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8.

A metallic rod of length ‘l’ is tied to a string of length 2l and made to rotate with angular speed ω on a horizontal table with one end of the string fixed. If there is a vertical magnetic field ‘B’ in the region, the e.m.f. induced across the ends of the rod is

D.

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9.

This question has Statement I and Statement II. Of the four choices given after the Statements, choose the
one that best describes the two Statements.
Statement – I: A point particle of mass m moving with speed v collides with stationary point particle of mass M. If the maximum energy loss possible is given as f
Statement – II : Maximum energy loss occurs when the particles get stuck together as a result of the collision.

• Statement – I is true, Statement – II is true, Statement – II is a correct explanation of Statement – I.

• Statement – I is true, Statement – II is true, Statement – II is not a correct explanation of Statement – I.

• Statement – I is true, Statement – II is false.

• Statement – I is false, Statement – II is true

D.

Statement – I is false, Statement – II is true

Before collision, the mass is m and after collision, the mass is m+M
therefore, Maximum energy loss

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10.

The above p-v diagram represents the thermodynamic cycle of an engine, operating with an ideal monoatomic gas. The amount of heat extracted from the source in a single cycle is

• povo

• 4povo

B.

Heat is extracted from the source in path DA and AB is

565 Views

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