MCQ-1

                                            

1)

When a block of mass M is suspended by a long wire of 

length L, the length of the wire becomes (L + l). The 

elastic potential energy stored in the extended wire is :

     (1)  Mgl

     (2)  MgL

   (3) ½ Mgl 

     (4) ½ MgL

    

EXPLANATION :

2)

A mass (m) is attached to a thin wire and whirled in a 

vertical circle. The wire is most likely to break when:

(1) the mass is at the highest point

(2) the wire is horizontal

(3) the mass is at the lowest point

(4) inclined at an angle of 60° from vertical

EXPLANATION :

3)

Ionized hydrogen atoms and a-particles with same 

momenta enters perpendicular to a constant magnetic 

field, B. The ratio of their radii of their paths rH : ra will

 be :

(1) 2 : 1

(2) 1 : 2

(3) 4 : 1

(4) 1 : 4

EXPLANATION :

4)

Body A of mass 4m moving with speed u collides with 

another body B of mass 2m, at rest. The collision is head 

on and elastic in nature. After the collision the fraction 

of energy lost by the colliding body A is :

   (1) 1/9

  (2) 8/9

  (3) 4/9
  (4) 5/9

    

EXPLANATION :

5) In a double slit experiment, when light of wavelength

 400 nm was used, the angular width of the first minima 

formed on a screen placed 1 m away, was found to be 0.2°.

What will be the angular width of the first minima, if the

entire experimental apparatus is immersed in water? (mwater= 4/3)

(1) 0.266°

(2) 0.15°

(3) 0.05°

(4) 0.1°  

EXPLANATION :