The binding energies of the nuclei A and B are $E_a and E_b$ respectively. Three atoms of the element B fuse to give one atom of element A and an energy Q is released. Then $E_a, E_b$ and Q are related as:

1. $E_a-3E_b=Q$ 

2. $3E_b-E_a=Q$

3. $E_a+3E_b=Q$ 

4. $E_b+3E_a=Q$

The radius of a nucleus of a mass number A is directly proportional to [MH CET 1999; AMU (En.) 2001; UPSEAT 2004; DUMET 2010]

1. $A^3$ 

2. A 

3. $A^{2/3}$

4. $A^{1/3}$

Which of the following statements is true for nuclear forces? [1990]

1. They obey the inverse square law of distance.

2. They obey the inverse third power law of distance.

3. They are short range forces.

4. They are equal in strength to electromagnetic forces.

The mass density of a nucleus varies with mass number A as [1992]

1. $A^2$

2. A 

3. Constant 

4. $\frac{1}{A}$