A \(5 kg\) uniform plank is balanced horizontally on a support by two weights attached to its ends. The plank is \(2 m\) long and the support is placed at \(0.5 m\) from one end. If the mass near the support is \(10 kg\), what mass must be placed at the other end?
A. 10 kg B. 20 kg C. 5 kg D. 15 kg
Correct Answer: C
Explanation
We take moment about the pivot i.e. Sum of clockwise moment = Sum of anticlockwise moment \(\Rightarrow 10 \times 0.5=5 \times 0.5+W_{2} \times 1.5\) \(10=2.5+1.5 W_{2}\) \(7.5=1.5 W_{2}\) \(W_{2}=7.5 / 1.5=5 kg\)
