Problem $3$

The person shown below is executing a standing leg lift. This person is $165$ cm height and $60$ kg weight. The stretching band has stiffness of $50\frac{N}{m}$ and it is activated when the foot is $5$ cm above ground. This band is attached to the foot at its center of mass. During movement, the foot is always horizontal, and the lower leg is always vertical, hence to maintain a complete attachment with the band. The angle of the thigh with the vertical $()$ varies from $0$ to $90$ according to the following equation,

$=9t$

Estimate the torque required at the hip joint as related to time $(t).$