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Units and Measurements · Question 24

JEE Main 2026 (Online) 23rd January Evening ShiftNumericalMedium📈 Topic in 19% papers+4
1

A ball of radius r and density dropped through a viscous liquid of density and viscosity attains its terminal velocity at time t, given by t = A a rb c d, where A is a constant and a, b, c and d are integers. The value of b + ca + d is .

Answer

1

Solution

Dimensions: [ ] = [ ] = ML-3, [r] = L, [ ] = ML-1T-1

T = ( ML-3)a+d Lb ( ML-1T-1)c

T: -c = 1 c = -1

M: a + d + c = 0 a + d = 1

L: -3(a + d) + b - c = 0 b = 3 - 1 = 2

b + ca + d = 2 - 11 = 1

(Check: time constant = m6 r = 2 r29 , i.e. a = 1, b = 2, c = -1, d = 0.)

Answer: 1

JEE Main 2026 (Online) 23rd January Evening Shift

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