GATE 2021 IN – Question 49
The electrically conductive square-section bar shown rests on a plane. Its mass is 1 kg and depth along y is 0.5 m. Friction coefficient is 0.1 and gravity 10 m/s$^2$. A uniform field is $\mathbf B=-1\hat z$ T. At $t=0$, current 10 A is switched on and maintained. After moving 1 m, its speed is ______ m/s (one decimal place).
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Correct answer: 2.7 to 2.9
Explanation
The electromagnetic force magnitude is ILB=10·0.5·1=5 N, along the surface. Sliding friction is μmg=0.1·1·10=1 N, so net force is 4 N and acceleration magnitude is 4 m/s². Starting from rest over 1 m, v=√(2as)=√8=2.828, rounded **2.8 m/s**.