Which instrument records seismic waves? MCQ with Answer and Explanation

Explanation:
v ∝ 1/√r. If r' = 2r, v' = v/√2. Orbital velocity decreases with increasing radius. Memory aid: 'Higher orbit ⇒ slower speed; v ∝ r⁻¹/²'. Proportional reasoning question testing gravitation formula application, frequently appearing in competitive exams without heavy calculation.

Explanation:
High resistance produces more heat (I²R), low melting point ensures quick melting. Both true and R explains A.

Explanation:
Leading zeros (before first non-zero digit) are not significant. So 0.0034060: the first non-zero is 3, then 4,0,6 are significant, and the trailing zero after decimal is significant. Thus significant digits are 3,4,0,6,0 — 5 digits. Note: The last zero indicates precision. Answer is 5.