A block of mass 5 k g is (i) pushed in case A and (ii) pulled in case B , by a force F = 20 N , making an angle of 30 o with the horizontal, as shown in the figures. The coefficient of friction between the block and floor is μ = 0.2 . The difference between the accelerations of the block, in case B and case A will be: g = 10 m s - 2

Question

A block of mass 5 k g is (i) pushed in case A and (ii) pulled in case B , by a force F = 20 N , making an angle of 30 o with the horizontal, as shown in the figures. The coefficient of friction between the block and floor is μ = 0.2 . The difference between the accelerations of the block, in case B and case A will be: g = 10 m s - 2, 3.2 m s - 2, 0 m s - 2, 0.8 m s - 2, 0.4 m s - 2

MARKS App · Accepted Answer

For Block A: N = m g + F sin ⁡ 30 ° = 5 × 10 + 20 × 1 2 = 60 N f r = 0.2 60 = 12 N F cos ⁡ 30 ° – f r = m a 20 3 2 - 12 = 5 × a ⇒ a A = 10 3 - 12 5 ……(i) For Block B: F sin ⁡ 30 ° + N = m g N = 5 × 10 – 20 × 1 2 = 40 N f r = 0.2 × 40 = 8 N F c o s 30 ° – f r = m a 20 3 2 - 8 = 5 × a ⇒ a B = 10 3 - 8 5 a B - a A = 4 5 = 0.8 m / s 2

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