Answer
$M=228N$
Work Step by Step
We choose the axis of rotation to be at the knee joint.
- The weight of the leg $W$ produces a clockwise (negative) torque. The lever arm is $(0.1m+0.15m)\cos30=(0.25m)\cos30$
- $M$ produces a counterclockwise (positive) torque. The lever arm is $(0.1m)\sin25$
The leg is in equilibrium, so these 2 torques balance each other.
$$W(0.25m)\cos30=M(0.1m)\sin25$$ $$M=\frac{44.5N(0.25m)\cos30}{(0.1m)\sin25}=228N$$
