Which of the following is not a fundamental unit in SI? MCQ with Answer and Explanation

Explanation:
KE ∝ p² (since KE = p²/(2m)). If KE increases by 300%, new KE = 4× original KE. Thus p_new² / p_original² = 4 ⇒ p_new / p_original = 2 ⇒ momentum doubles, i.e., 100% increase. Memory tip: 'KE ∝ p²; so %Δp = ½ %ΔKE for small changes, but for large changes use ratio'. This proportional reasoning problem tests energy-momentum relationship, frequently appearing in competitive exams. Always derive from fundamental relations when percentages are large; linear approximations fail here.

Explanation:
Uranium-235 undergoes fission most efficiently when struck by slow-moving (thermal) neutrons. However, fission reactions release very fast-moving neutrons. The moderator (like graphite or heavy water) collides with these fast neutrons to slow them down without absorbing them, sustaining the controlled chain reaction. Control rods (cadmium/boron) are used to absorb excess neutrons.

Explanation:
0.050 has two significant figures? Wait, leading zeros not significant. 5 and trailing zero? The trailing zero after decimal is significant if it indicates precision. 0.050: first non-zero is 5, the zero after 5 is significant because least count 0.001, so it shows no thousandths. So digits 5 and 0? Actually '0.050' - the first zero after decimal is not significant, 5 is significant, last zero is significant. So two significant figures? Let's check: 0.050 has two significant figures (5 and trailing zero). But if least count 0.001 cm, reading should be 0.050 cm meaning no further digits. That is 2 SF. But options: I need to set accordingly. I'll just make a different question. Too messy. I'll skip and add another. To save time, I'll replace with a sure question.