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The coefficient of static friction, μs\mu_s, between block A of mass 2 kg and the table as shown in the figure is 0.2. What would be the maximum mass value of block B so that the two blocks do not move? The string and the pulley are assumed to be smooth and massless. (g=10 m/s2g = 10 \text{ m/s}^2)

A

2.0 kg

B

4.0 kg

C

0.2 kg

D

0.4 kg

Step-by-Step Solution

  1. System Analysis: Block A is on a horizontal surface, held in place by the static friction. Block B is hanging and provides the tension in the string trying to pull Block A. For the blocks not to move, the system must be in equilibrium.
  2. Forces on Block B: The tension TT in the string supports the weight of Block B. T=mBgT = m_B g
  3. Forces on Block A: The tension TT pulls Block A horizontally. This is opposed by the static friction force fsf_s. The normal reaction on A is N=mAgN = m_A g. For equilibrium: T=fsT = f_s
  4. Limiting Condition: The maximum mass of B corresponds to the maximum tension Block A can withstand without sliding. This occurs when static friction reaches its limiting value: (fs)max=μsN=μsmAg(f_s)_{max} = \mu_s N = \mu_s m_A g [Source 56, 63].
  5. Calculation: Equating tension to limiting friction: mBg=μsmAgm_B g = \mu_s m_A g mB=μsmAm_B = \mu_s m_A mB=0.2×2 kg=0.4 kgm_B = 0.2 \times 2 \text{ kg} = 0.4 \text{ kg}
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