Calculating force of the femur on the knee cap.

  • Thread starter meaganl
  • Start date
  • Tags
    Force
In summary, the diagram of the leg shows the femur and tibia, with the quadriceps muscle applying a force to the lower leg via a tendon embedded with the kneecap. The simplified model of the leg shows the leg bones represented by beams attached by a pin, the tendon modeled by a rope, and the kneecap acting as a pulley. Using the equations fnet=ma, Fx= max, and Fy=may, the x component of the force of the femur on the kneecap is approximately 191.4N and the y component is approximately -1.67N.
  • #1
meaganl
4
0

Homework Statement


The diagram of the leg shows the femur (1) and tibia (2). The quadriceps muscle (3) applies a force to the lower leg via a tendon (4) that is embedded with the kneecap (5). If the force applied by the muscle to the tendon is FM = 420 N, what is the force of the femur on the kneecap? A simplified model of the leg is shown next to the diagram. The leg bones are represented by two beams attached by a pin. The tendon is modeled by a rope and the kneecap acts like a pulley. The tendon above the kneecap makes an angle θ1 = 23° with respect to the vertical, and the portion of the tendon below the kneecap makes an angle of θ2 = 24° with respect to the vertical. Enter the x component, followed by the y component.

knee.gif



Homework Equations



fnet=ma



The Attempt at a Solution



I tried:

Fx= max
T1x + T2x + Ffemurx=0
-240sin23 -240sin24 + Ffemur= 0
-93.78 - 97.62 + Ffemur=0
Ffemur= 191.4N

Fy=may
T1y + T2y + Ffemury=0
240cos23 - 240cos24 + Ffemury=0
220.92 - 219.25 + Ffemury=0
Ffemury= -1.67N

I didn't get the right answer..

please help!
 
Physics news on Phys.org
  • #2
Supposed that the tension is the same all along the tendon, and x means horizontal , y means vertical component of force, your solution looks correct. Try to use less significant digits.

ehild
 

1. How is the force of the femur on the knee cap calculated?

The force of the femur on the knee cap is calculated by multiplying the weight of the body above the knee with the ratio of the length of the femur to the length of the knee cap.

2. What is the relationship between the force of the femur and the knee cap?

The force of the femur on the knee cap is directly proportional to the weight of the body above the knee. This means that as the weight increases, the force of the femur on the knee cap also increases.

3. Can the force of the femur on the knee cap be measured?

Yes, the force of the femur on the knee cap can be measured using specialized equipment such as force plates or pressure sensors. These devices can accurately measure the force exerted on the knee cap by the femur during movement.

4. How does the angle of the knee joint affect the force of the femur on the knee cap?

The angle of the knee joint can greatly affect the force of the femur on the knee cap. When the knee is at a 90 degree angle, the force exerted by the femur is at its maximum. However, as the angle increases or decreases, the force decreases accordingly.

5. Are there any factors that can affect the force of the femur on the knee cap?

Yes, there are several factors that can affect the force of the femur on the knee cap. These include body weight, muscle strength, and joint stability. Additionally, activities such as running or jumping can also increase the force exerted on the knee cap by the femur.

Similar threads

Finding the force of the femur on the knee cap.
    • Introductory Physics Homework Help
Replies
2
Views
5K

Hot Threads

Recent Insights

Back
Top