(A) The acceleration of S is always directed towards the centre of the earth.

(B) The angular momentum of S about the centre of the earth changes in direction, but its magnitude remain constant

(C) the total mechanical energy of S varies periodically with time

(D) The linear momentum of S remains constant in magnitude

2. The torque

**r**on a body about a given point is found to be equal to

**A**×

**L**where

**A**is a constant vector and

**L**is the angular momentum of the body about that point. From this it follows that:

(A) (

**dL**)/dt is perpendicular to

**L**at all instants of time.

(B) the component of

**L**in the direction of

**A**does not change with time.

(C) the magnitude of

**L**does not change with time.

(D)

**L**does not change with time.

3. In a p-n junction diode not connected to any circuit :

(A) the potential is the same everywhere

(B) the p-type side is at a higher potential than the n-type side

(C) there is an electric field at the junction directed from the n-side to the p-type side.

(D) there is an electric field at the junction directed from the p-type side to the n-type side.

4. During the melting of a slab of ice at 273K at atmospheric pressure :

(A) positive work is done by the ice-water system on the atmosphere.

(B) positive work is done on the ice-water system by the atmosphere.

(C) the internal energy of the ice-water system increases.

(D) the internal energy of the ice-water system decreases.

5. A spherical surface of radius of curvature R, separates air) refractive index 1.0) from glass (refractive index 1.5). The centre of curvature is in the glass. A point object P placed in air is found to have a real image Q in the glass. The line PQ cuts the surface at a point O and PO = OQ. The distance PO is equal to :

(A) 5R (B) 3R

(C) 2R (D) 1.5R

Source: 1998 JEE

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