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Saturday, 31 October

JEE Main 2021 · PhysicsMultiple choiceSingle correctMediumApplication

JEE Main 24 February 2021, Shift 1, Physics Q11

Question 11 of 90 in this shift, Physics question 11 of 30, Section A.

In the given figure, a mass M is attached to a horizontal spring which is fixed on one side to a rigid support. The spring constant of the spring is k. The mass oscillates on a frictionless surface with time period T and amplitude A. When the mass is in equilibrium position, as shown in the figure, another mass m is gently fixed upon it. The new amplitude of oscillation will be :

The figure, in words

A block labelled M rests on a horizontal hatched surface; a smaller block labelled m sits on top of M. M is connected on its right side by a horizontal spring labelled k to a vertical hatched rigid wall on the right.
  1. (1)AM+mMA\sqrt{\frac{M+m}{M}}
  2. (2)AMM+mA\sqrt{\frac{M}{M+m}}Official answer
  3. (3)AM−mMA\sqrt{\frac{M-m}{M}}
  4. (4)AMM−mA\sqrt{\frac{M}{M-m}}

Official answer

Option 2

NTA final key.

Chapter
Oscillations
Topic
Energy in SHM
Idea tested
Mass Dropped at Mean Position

Same idea in other shifts

Asked 3× in all
  1. 27 Jul 2022, Shift 1 · Q57A mass 0.9 kg, attached to a horizontal spring, executes SHM with an amplitude A1A_1. When this mass passes through its mean position,…MediumNumerical value
  2. 3 Sep 2020, Shift 2 · Q9A block of mass m attached to a massless spring is performing oscillatory motion of amplitude 'A' on a frictionless horizontal plane. If…MediumSingle correct

Question text from the official JEE Main paper published by NTA; answer from the final answer key. Chapter, topic and idea tags, difficulty and skill are Lumi’s. This question needs a figure we do not reproduce; it is described in words above. Lumi analyses 108 of the 174 JEE Main shifts held from 2017 to 2026.