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NEET PHYSICSLAWS OF MOTIONEasy

Question

Three blocks of masses m1m_1, m2m_2 and m3m_3 are connected by massless strings as shown on a frictionless table. They are pulled with a force T3=40 NT_3 = 40 \text{ N}. If m1=10 kgm_1 = 10 \text{ kg}, m2=6 kgm_2 = 6 \text{ kg} and m3=4 kgm_3 = 4 \text{ kg}, the tension T2T_2 will be:

A

20 N

B

40 N

C

10 N

D

32 N

Step-by-Step Solution

  1. System Acceleration: The three blocks move together with a common acceleration aa. The total mass of the system is M=m1+m2+m3M = m_1 + m_2 + m_3. Applying Newton's Second Law to the entire system: a=Net ForceTotal Mass=T3m1+m2+m3a = \frac{\text{Net Force}}{\text{Total Mass}} = \frac{T_3}{m_1 + m_2 + m_3} Substituting the values: a=4010+6+4=4020=2 m/s2a = \frac{40}{10 + 6 + 4} = \frac{40}{20} = 2 \text{ m/s}^2.
  2. Isolating the Sub-system: The tension T2T_2 is the force pulling the blocks m1m_1 and m2m_2. (Assuming the arrangement is m1m2m3m_1 - m_2 - m_3 with force applied on m3m_3). Alternatively, if T2T_2 is the tension between m2m_2 and m3m_3, it pulls the mass (m1+m2)(m_1 + m_2).
  • Case 1 (Standard): T2T_2 pulls m1m_1 and m2m_2. Then T2=(m1+m2)a=(10+6)×2=32 NT_2 = (m_1 + m_2)a = (10 + 6) \times 2 = 32 \text{ N}.
  • Case 2: If T2T_2 were between m1m_1 and m2m_2, it would pull only m1m_1. Then T2=m1a=10×2=20 NT_2 = m_1 a = 10 \times 2 = 20 \text{ N}.
  1. Conclusion: Given the probable answer is 32 N, the tension T2T_2 refers to the string connecting m2m_2 and m3m_3, which pulls the combined mass of m1m_1 and m2m_2 behind it. T2=(m1+m2)a=16×2=32 NT_2 = (m_1 + m_2)a = 16 \times 2 = 32 \text{ N} (Reference: NCERT Class 11, Physics Part I, Chapter 5: Laws of Motion, Section 5.10).

Exam Context & Concepts Covered

This question aligns with the NEET PHYSICS syllabus, specifically targeting concepts from LAWS OF MOTION. Mastering this topic is crucial for scoring well in the upcoming medical entrance examinations. Solving conceptually related problems will help you understand the nuances of these concepts and improve your problem-solving speed.

PHYSICSLAWS OF MOTIONblocksmassesconnectedmasslessstrings

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