Question

Let $F_{pp},F_{pn},$ and $F_{nn},$ denote the magnitudes of net force by a proton on a proton, by a proton on a neutron and by a neutron on a neutron respectively. Neglect gravitation force. When the separation is 1 fm:

• A. $F_{pp}>:F_{pn}=F_{nn}$
• B. $F_{pp}=:F_{pn}=F_{nn}$
• C. $F_{pp}>:F_{pn}>F_{nn}$
• D. $F_{pp}<:F_{pn}=F_{nn}$

Answer 1

Answer: (D)

$F_{pp}<:F_{pn}=F_{nn}$

Neutron is the neutral particle. Hence, the net force of neutron on neutron and proton on neutron is equal.
When two positively charged protons approach each other, both repel each other. Hence the net force of a proton on proton is lower than the net force of proton on neutron.