**Ques:** A sample contains 16 *gm* of a radioactive material, the half life of which is two days. After 32 days, the amount of radioactive material left in the sample is

(a) Less than 1 *mg*

(b) ¼ gm

(c) ½ gm

(d) 1 *gm
*Ans. (a)

**Question: **The elongation of a freely hanging uniform steel rope, if its length is doubled, will increase in the ratio of

(a) 2 : 1

(b) 4 : 1

(c) 8 : 1

(d) 16 : 1

**Question: **A 1 meter long sonometer wire is fixed at both ends and a bridge is placed at one-tenth of length of wire from one of its ends. It is set into transverse vibrations. The velocity of the wave in the wire if the frequency is 400 Hz, is

(a) 40 m/s

(b) 40 m/s

(c) 100 m/s

(d) 120 m/s

**Question: **Sound waves of frequency 600 Hz fall normally on a perfectly reflecting wall. The distance from the wall at which the air particles have the maximum amplitude of vibration is (speed of sound in air = 330 m/s)

(a) 13.75 cm

(b) 41.25 cm

(c) 68.75 cm

(d) All of the above

**Related:** Question Bank for Probability (Maths)

**Question: **A slab of glass, of refractive index 1.5 and thickness 6 cm, is placed in front of a concave mirror, the faces of the slab being perpendicular to the principal axis of the mirror. If the radius of curvature of the mirror is 40 cm and the reflected image coincides with the object, then the distance of the object from the mirror is

(a) 30 cm

(b) 22 cm

(c) 42 cm

(d) 28 cm

**Question: **An electron in a hydrogen atom makes a transition from first excited state to ground state. The equivalent current due to circulating electron

(a) increases 2 times

(b) increases 4 times

(c) increases 8 times

(d) remains the same

**Question: **A double slit of separation 0.1 cm is illuminated by while light. A coloured interference pattern is formed on a screen 100 cm away. If a pin hole is located in this screen at a distance of 2 mm from the central fringe, the wavelengths in the visible spectrum which will be absent in the light transmitted through the pin-hole are

(a) 5714 Å and 4444 Å

(b) 6000 Å and 5000 Å

(c) 5500 Å and 4500 Å

(d) 5200 Å and 4200 Å

**Question: **A body of mass 10 kg is moving along a circular path of radius 100m. Its speed increases, in a uniform manner, from 17 m/s to 26m/s in a time duration of 3s. Force acting on the body when it is travelling at a speed 20 m/s is

(a) 45 newton

(b) 42.5 newton

(c) 47.5 newton

(d) 50 newton

**Question: **A lens of unknown nature (convex/concave) and of focal length 20 cm forms an erect image 4 times the size of an object. Determine the nature of lens and also the distance of object from the lens.

(a) convex, 15 cm

(b) convex, 40 cm

(c) concave, 15 cm

(d) concave, 40 cm

**Related:** thermodynamics question bank with answers

**Question: **A capacitor is charged to potential *E *by a cell of emf *E*. If an identical capacitor is inserted in the circuit in series with the previous capacitor, the potential difference across the new capacitor is

(a) 2*E
*(b)

*E*

(c)

*E*/2

(d) zero

**Question: **A train is uniformly accelerated and passes successive kilometer stones, wjjh velocities of 18 kmph and 36 kmph respectively. The velocity, when it passes the next kilometer stone is approximately

(a) 48 kmph

(b) 54 kmph

(c) 60 kmph

(d) 72 kmph

**Question: **An infinite number of masses, each of 1 kg, are placed on the positive .v-axis at Im, 2m, 4m, 8m, … from the origin. The magnitude of the gravitational field at the origin due to this distribution of masses is

{G: Universal gravitational constant)

(a) G

(b) 4/3 G

(c) 4/9 G

(d) none of these

**Question: **A transverse wave travels along a string of material of specific gravity 10. If maximum particle velocity is one-tenth of wave velocity v, then intensity of the wave in the string (in SI units) is

(a) 0.05 V^{3}

(b) 5v^{3}

(c) 5OV^{3}

(d) 5 x 10^{5} V^{3}

**Question: **A standing wave is produced in a vapour of a chemical of atomic mass (127 g mol^{–1}) at 400 K. Nodes are found to be 9.57 cm apart when frequency of source was 1000 Hz. The vapour used for the experiment is (R = 8.31 JK^{–1}mol^{–1})

(a) monatomic

(b) diatomic

(c) polyatomic

(d) cannot determine

**Related:** Permutation and Combination Mock Test

**Question: **A copper wire having resistance 0.01 ohm in each metre is used to wind a 400 turn solenoid of radius 1 cm and length 20 cm. Find the emf of the battery which when connected across the solenoid will produce a

magnetic field 1 x 10^{–2} Tesla at the centre of solenoid.

(a) 1 volt

(b) 2 volts

(c) 2.5 volts

(d) 3 volts

**Question: **The potential energy of a particle varies with position x according to the relation U(x) = x^{3} – 4x. The point x = 2 is a point of

(a) stable equilibrium

(b) unstable equilibrium

(c) neutral equilibrium

(d) none of the above

**Question: **A body is sliding down an inclined plane having coefficient of friction 0.5. If the normal reaction is twice that of the resultant downward force along the incline, the angle between the inclined plane and the horizontal

is

(a) 15°

(b) 30°

(c) 45°

(d) 60°

**Question: **The frequency of a sonometer wire is *f*. The frequency becomes *f*/2 when the mass producing the tension is completely immersed in water and on immersing the mass in a certain liquid, frequency becomes *f*/3. The relative density of the liquid is

(a) 1.32

(b) 1.03

(c) 1.41

(d) 118

**Related:** fungi multiple choice questions

**Question: **What is the ratio of *de-Broglie* wavelengths of electron in the second and third Bohr orbits in hydrogen atom

(a) 2/3

(b) 3/2

(c) 4/3

(d) 3/4

**Ques:** A radioactive substance has a half life of 60 *minutes*. After 3 *hours*, the fraction of atom that have decayed would be

(a) 12.5%

(b) 87.5%

(c) 8.5%

(d) 25.1%

Ans. (b)

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