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Saturday, 31 October

JEE Main 2025 · PhysicsMultiple choiceOtherHardMulti-step

JEE Main 3 April 2025, Shift 1, Physics Q36

Question 36 of 75 in this shift, Physics question 11 of 25, Section A.

Two blocks of masses m and M, (M>m)(M > m), are placed on a frictionless table as shown in figure. A massless spring with spring constant k is attached with the lower block. If the system is slightly displaced and released, then (μ\mu = coefficient of friction between the two blocks) A. The time period of small oscillation of the two blocks is T=2π(m+M)kT = 2\pi\sqrt{\frac{(m+M)}{k}} B. The acceleration of the blocks is a=−kxM+ma = -\frac{kx}{M+m} (xx = displacement of the blocks from the mean position) C. The magnitude of the frictional force on the upper block is mμ∣x∣M+m\frac{m\mu|x|}{M+m} D. The maximum amplitude of the upper block, if it does not slip, is μ(M+m)gk\frac{\mu(M+m)g}{k} E. Maximum frictional force can be μ(M+m)g\mu(M+m)g. Choose the correct answer from the options given below:

The figure, in words

Block m (with friction coefficient mu between blocks) sits on block M; M is attached to a wall by a spring of constant k on a frictionless table.
  1. (1)A, B, C Only
  2. (2)B, C, D Only
  3. (3)C, D, E Only
  4. (4)A, B, D OnlyOfficial answer

Official answer

Option 4

NTA final key.

Chapter
Oscillations
Topic
SHM Equations
Idea tested
SHM Definition and Force Law

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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.