Verified Solution • 2025–26 Session moderate

QJEEM21Ph34ae: JEE Main 2021 Physics - Class 11 JEEM21Ph34ae Solution: Two masses A and B, each of mass M are fixed together by a…

Two masses A and B, each of mass M are fixed together by a massless spring. A force acts on the mass B as shown in the figure. If the mass A starts moving away from mass B with acceleration 'a', then the acceleration of mass B will be :

JEE Main 2021 (Online) 26th February Evening Shift Physics - Laws of Motion Question 85 English

Multiple Choice Options

  • A MFF+Ma
  • B F+MaM
  • C Ma−FM
  • D F−MaM

Step-by-Step Verified Solution

Let spring force acting on the both block is Fs.

F.B.D. of Block A

JEE Main 2021 (Online) 26th February Evening Shift Physics - Laws of Motion Question 85 English Explanation 1

∴ Fs = Ma ..... (i)

F.B.D. of Block B,

JEE Main 2021 (Online) 26th February Evening Shift Physics - Laws of Motion Question 85 English Explanation 2

∴ Acceleration of Block B,

a1=FnetM=F−FsM=F−MaM

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