A uniform rod of length 1 m and mass 4 kg is supported on two knife-edges placed 10 cm from each end. A 60 N weight is suspended at 30 cm from one end. The reactions at the knife edges is

Question

A uniform rod of length 1 m and mass 4 kg is supported on two knife-edges placed 10 cm from each end. A 60 N weight is suspended at 30 cm from one end. The reactions at the knife edges is (A) 60 N, 40 N (B) 75 N, 25 N (C) 65 N, 35 N (D) 55 N, 45 N

Tardigrade Admin · Accepted Answer

<img class="img-fluid question-image" alt="image" src="https://cdn.tardigrade.in/img/question/physics/d6fe0a329b5873f0cfd193c8502428f6-.png" /> AB is the rod. K1 and K2 are the two knife edges. Since the rod is uniform, therefore its weight acts at its centre of gravity G. Let R1 and R2 be reactions at the knife edges. For the translational equilibrium of the rod, R1 + R2 - 60 N - 40 N = 0 R1 + R2 = 60 N + 40 N = 100 N ... (i) For the rotational equilibrium, taking moments about G, we get -R1(40) + 60(20) + R2(40) = 0 R1 - R2 = (1200/40) = 30 N ...(ii) Adding (i) and (ii), we get 2R1 = 130 N or R1 = 65 N Substituting this value in Eq. (i), we get R2 = 35 N

Q. A uniform rod of length $1 m$ and mass $4 k g$ is supported on two knife-edges placed $10 c m$ from each end. A $60 N$ weight is suspended at $30 c m$ from one end. The reactions at the knife edges is

$60 N, 40 N$

$75 N, 25 N$

$65 N, 35 N$

$55 N, 45 N$

Q. A uniform rod of length 1m and mass 4kg is supported on two knife-edges placed 10cm from each end. A 60N weight is suspended at 30cm from one end. The reactions at the knife edges is

60N,40N

75N,25N

65N,35N

55N,45N

Q. A uniform rod of length $1 m$ and mass $4 k g$ is supported on two knife-edges placed $10 c m$ from each end. A $60 N$ weight is suspended at $30 c m$ from one end. The reactions at the knife edges is

$60 N, 40 N$

$75 N, 25 N$

$65 N, 35 N$

$55 N, 45 N$