Question

If you pull with your lower leg such that you exert a 90 N force on the cord attached to your ankle, determine the magnitude of the tension force of your hamstring on your leg and the compression force at the knee joint.

Answer 1

This question is incomplete, the missing diagram is uploaded along this answer below.

Answer:

- the magnitude of the tension force exerted by the hamstring muscles on the leg is 990 N

- the magnitude of compression force at the knee joint is 900 N

Explanation:

Given the data in the question and diagram below;

Net torque = 0

Torque = force × lever arm

so

F$_{ConF$  × ( 15.0 in + 1.5 in ) = T$_{HonL$ × 1.5 in

given that F$_{ConF$ = 90 N

90 × ( 15.0 in + 1.5 in ) = T$_{HonL$ × 1.5 in

90 N × 16.5 in =  T$_{HonL$ × 1.5 in

T$_{HonL$ = ( 90 N × 16.5 in ) / 1.5 in

T$_{HonL$ = 990 N

Therefore, the magnitude of the tension force exerted by the hamstring muscles on the leg is 990 N

b) magnitude of compression force at the knee joint;

In equilibrium, net force = 0

along horizontal

F$_{FonB$ - T$_{HonL$ + F$_{ConF$ = 0

we substitute

F$_{FonB$ - 990 + 90 = 0

F$_{FonB$ - 900 = 0

F$_{FonB$ = 900 N

Therefore, the magnitude of compression force at the knee joint is 900 N