An athlete is supporting a weight of 200N in his hand with his forearm at a right angle to his biceps.
Assuming his biceps are in the vertical plane, the axis of rotation of the forearm is 3cm from the elbow
and 25cm from the centre of gravity of the weight, calculate the force that must be produced by the
biceps to hold the weight.
To solve for the force that must be produced by the biceps to hold the weight, we can set up a torque equation. Torque is defined as the product of force and the perpendicular distance from the axis of rotation to the line of action of the force.
The torque produced by the weight is given by:
Torque(weight) = weight * distance from the weight to the axis of rotation = 200N * 25cm = 5000 N*cm
The torque produced by the force from the biceps is given by:
Torque(biceps) = force from biceps * distance from the biceps to the axis of rotation = F * 3cm
Since the athlete is holding the weight at a right angle to his biceps, the torques produced by the weight and the force from the biceps must be equal to keep the weight balanced:
Torque(weight) = Torque(biceps)
5000 N*cm = F * 3cm
F = 5000 N*cm / 3cm
F = 1666.67 N
Therefore, the force that must be produced by the biceps to hold the weight is approximately 1666.67N.