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A block of mass m is placed on the top of a 6 kg cart such that the time period of the system is 0.75 s assuming there is no slipping.  If the cart is displaced by 50 mm from its equilibrium position and released, then the coefficient of static friction μs between block and cart is just sufficient to prevent the block from sliding. The value of m and μs respectively are (Take g=9.8 m/s2)

PhysicsOscillationsJEE Main
Options:
  • A 1.63kg; 0.251
  • B 2.55kg; 0.385
  • C 3.42kg; 0.632
  • D 4.28kg; 0.876
Solution:
1544 Upvotes Verified Answer
The correct answer is: 2.55kg; 0.385
T = 2 π m + 6 600                   ( T = 2 π m k )

or 0.75 = 2 π m + 6 600

m = 0.75 2 × 600 2 π 2 - 6

                          = 2.55 kg

Maximum acceleration of SHM is,

amax = ω2A   (A = amplitude)

i.e., maximum force on mass 'm' is m ω2 A which is being provided by the force of friction between the mass and the cart. Therefore,

              μsmg  ≥  mω2 A

or           μ s ω 2 A g

or           μ s ( 2 π T ) 2 · A g

or           μ s ( 2 π 0.75 ) 2 ( 0.05 9.8 ) A = 50 mm

or               μs   ≥  0.358

Thus, the minimum value of  μs should be 0.358.

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