Answer
The correct answer is:
B. $6.5\times 10^{-7}~N$
Work Step by Step
Since the system is in equilibrium, the torques about the fulcrum must be equal in magnitude. We can find the downward force $F$:
$r_L~F = r_R~mg$
$(0.60~m)~F = (0.40~m)~(1.0\times 10^{-7}~kg)(9.80~m/s^2)$
$F = \frac{(0.40~m)~(1.0\times 10^{-7}~kg)(9.80~m/s^2)}{0.60~m}$
$F = 6.5\times 10^{-7}~N$
The correct answer is:
B. $6.5\times 10^{-7}~N$
