Which of the following forces is/are fundamental in nature? 1. Gravitational force 2. Electromagnetic forces 3. Strong and weak nuclear forces Select the correct answer using the code given below:
- (a)1 only
- (b)1 and 2 only
- (c)2 and 3 only
- (d)1, 2 and 3
Correct — D, 1, 2 and 3. Modern physics recognises exactly four fundamental interactions: the gravitational, the electromagnetic, the strong nuclear and the weak nuclear force. Statement 1 names the gravitational force, statement 2 the electromagnetic force, and statement 3 groups the strong and weak nuclear forces — the remaining two. Between them the three statements cover all four fundamental forces, so each one is fundamental and the correct code is 1, 2 and 3.
- (a)1 only — Choosing gravity alone wrongly excludes the electromagnetic force and the two nuclear forces, which are just as fundamental. Gravity is only one of the four fundamental interactions.
- (b)1 and 2 only — This leaves out the strong and weak nuclear forces, which are genuinely fundamental — they act inside the atomic nucleus and cannot be derived from gravity and electromagnetism.
- (c)2 and 3 only — This drops gravity. Although gravity is by far the weakest of the four, it is still one of the four fundamental forces of nature, so it must be included.
All known forces in nature reduce to four fundamental interactions: the strong nuclear force, the electromagnetic force, the weak nuclear force and the gravitational force. Everyday forces such as friction, tension and normal reaction are not new fundamental forces — they are large-scale outcomes of the electromagnetic interaction between atoms.
The item simply asks which listed forces are fundamental, and all three statements name fundamental forces, so the widest option is right. The trap is to drop gravity because it feels 'ordinary', or to drop the nuclear forces because they are unfamiliar; both mistakes shrink the true count of four.
- There are four fundamental forces — strong nuclear, electromagnetic, weak nuclear and gravitational.
- In order of strength they run strong > electromagnetic > weak > gravitational, with gravity by far the weakest.
- The strong and weak nuclear forces act only over nuclear distances (about 10^-15 m); gravity and electromagnetism have unlimited range.
- Their carrier particles are the gluon (strong), the photon (electromagnetic) and the W and Z bosons (weak); gravity's carrier, the graviton, remains hypothetical.
- The weak force drives beta decay and radioactivity, while the strong force binds protons and neutrons inside the nucleus.
Gravitational, electromagnetic, strong and weak nuclear forces are the four fundamental interactions.
- Excluding gravity because it seems too everyday to be 'fundamental'.
- Excluding the nuclear forces because they are unfamiliar.
- Confusing derived contact forces (friction, tension) with new fundamental forces.
NDA/UPSC ask which forces are fundamental, or rank them by strength/range — remember the four (strong, electromagnetic, weak, gravitational) and that gravity is the weakest.
The known forces of nature can be divided into four classes, viz., gravity, electromagnetism, weak nuclear force and strong nuclear force. With reference to them, which one of the following statements is not correct?
- (a) Gravity is the strongest of the four
- (b) Electromagnetism acts only on particles with an electric charge
- (c) Weak nuclear force causes radioactivity
- (d) Strong nuclear force holds protons and neutrons inside the nucleus of an atom
Answer(a) Gravity is the strongest of the four — this is the statement that is NOT correct, since gravity is in fact the weakest of the four fundamental forces.
UPSC prelims 2013 tested the very same four fundamental forces, asking which statement about them is wrong — reinforcing that gravity, electromagnetism and the strong and weak nuclear forces are the fundamental interactions and that gravity is the weakest, not the strongest.
- practice — not a real PYQ
Which of the four fundamental forces of nature is the weakest?
- (a)Strong nuclear force
- (b)Electromagnetic force
- (c)Weak nuclear force
- (d)Gravitational force
Answer(d) Gravitational force — despite shaping planets and stars, it is by far the weakest of the four fundamental forces.
- practice — not a real PYQ
The fundamental force responsible for radioactive beta decay is the
- (a)strong nuclear force
- (b)weak nuclear force
- (c)electromagnetic force
- (d)gravitational force
Answer(b) weak nuclear force — it governs beta decay and other transformations of subatomic particles.