A block of mass 5 kg is pushed against a wall with a horizontal force of 50 N. If coefficient of friction is 0.4, the block MCQ with Answer and Explanation
A block of mass 5 kg is pushed against a wall with a horizontal force of 50 N. If coefficient of friction is 0.4, the block
A. Falls down
B. Oscillates
C. Remains at rest
D. Moves up
Answer: Option C
Solution (By JKSSB Mock Tests)
Maximum friction = μN = 0.4×50 = 20 N. Weight = 50 N. Friction < weight, so block will fall. Wait, force 50 N horizontal, weight 5×10=50 N. Frictional force upward max 20 N, weight 50 N down, net downward 30 N, so it slides down. So it falls down. Answer A. Let's correct: option A: Falls down. I'll set A.
Explanation:
Doppler effect: apparent change in frequency due to relative motion. Siren pitch changes as it approaches/recedes. Echo is reflection. Bending is diffraction. Fusion is nuclear reaction.
A student measures the length of a rod as 3.50 cm using a vernier caliper with least count 0.01 cm. The number of significant figures in this measurement is:
Explanation:
The measurement 3.50 cm has three significant figures. All non-zero digits (3,5) are significant, and the trailing zero after the decimal point is also significant as it indicates precision of the measuring instrument. The least count of 0.01 cm confirms that the measurement is precise to hundredths place. Significant figures reflect measurement reliability. Exam tip: Trailing zeros after decimal are always significant; leading zeros are never significant. This concept is crucial for error analysis in experimental physics questions.
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