A body falls freely from rest. The ratio of distances covered in 1st, 2nd, and 3rd seconds is MCQ with Answer and Explanation

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A body falls freely from rest. The ratio of distances covered in 1st, 2nd, and 3rd seconds is

A. 1:3:5

B. 1:2:3

C. 1:1:1

D. 1:4:9

Answer: Option A

Solution (By JKExamLibrary)

s_nth = u + (g/2)(2n-1). u=0 => s ∝ (2n-1). So 1, 3, 5. Classic kinematic ratio.

This question belongs to: Science Physics

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Question #1 Report Error

Which of the following prefix represents 10⁻¹⁵?

A. Nano

B. Pico

C. Atto

D. Femto

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Correct Answer: Option D

Explanation:
Femto (f) = 10⁻¹⁵. Pico (p) = 10⁻¹², nano (n) = 10⁻⁹, atto (a) = 10⁻¹⁸. The prefix chain: milli 10⁻³, micro 10⁻⁶, nano 10⁻⁹, pico 10⁻¹², femto 10⁻¹⁵, atto 10⁻¹⁸. Mnemonic: Femto is 'fifteen'.

This question belongs to: Science Physics

Question #2 Report Error

The force between two charges in vacuum is F. If a medium of dielectric constant 4 is introduced, force becomes

A. F/2

B. 2F

C. F/4

D. 4F

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Correct Answer: Option C

Explanation:
F_medium = F_vacuum / K.

This question belongs to: Science Physics

Question #3 Report Error

A spring stores 18 J energy when stretched 3 cm. Force constant k is:

A. 200 N/m

B. 40000 N/m

C. 6 N/m

D. 2 N/m

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Correct Answer: Option B

Explanation:
Elastic PE: U = ½kx² ⇒ k = 2U/x². x = 3 cm = 0.03 m. k = 2×18/(0.03)² = 36/0.0009 = 40000 N/m. Unit conversion critical: cm to m. Memory aid: 'k = 2U/x²; always use SI units'. Tests spring energy formula application with unit conversion, frequently appearing in competitive exams.

This question belongs to: Science Physics

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