Learning Materials
Features
Discover
Chapter 9: Q11 CQ (page 315)
Why are the forces exerted on the outside world by the limbs of our bodies usually much smaller than the forces exerted by muscles inside the body?
The limbs in the human body are the third-class lever.
Over 30 million students worldwide already upgrade their learning with 91影视!
All the tools & learning materials you need for study success - in one app.
Get started for free
The upper leg muscle (quadriceps) exerts a force of\({\rm{1250 N}}\), which is carried by a tendon over the kneecap (the patella) at the angles shown inFigure\({\rm{9}}{\rm{.38}}\). Find the direction and magnitude of the force exerted by the kneecap on the upper leg bone (the femur).
What is the mechanical advantage of a nail puller鈥攕imilar to the one shown inFigure\({\rm{9}}{\rm{.23}}\)鈥攚here you exert a force \({\rm{45}}\;{\rm{cm}}\)from the pivot and the nail is \({\rm{1}}{\rm{.8}}\;{\rm{cm}}\)on the other side? What minimum force must you exert to apply a force of \({\rm{1250}}\;{\rm{N}}\) to the nail?
Suppose a \({\rm{900}}\;{\rm{kg}}\)car is on the bridge inFigure\({\rm{9}}{\rm{.34}}\)with its center of mass halfway between the hinges and the cable attachments. (The bridge is supported by the cables and hinges only.) (a) Find the force in the cables. (b) Find the direction and magnitude of the force exerted by the hinges on the bridge.
Suppose the biceps muscle was attached through tendons to the upper arm close to the elbow and the forearm near the wrist. What would be the advantages and disadvantages of this type of construction for the motion of the arm?
Explain why the forces in our joints are several times larger than the forces we exert on the outside world with our limbs. Can these forces be even greater than muscle forces?
What do you think about this solution?
We value your feedback to improve our textbook solutions.
Explanations 
Textbooks 
Flashcards 
91影视 AI 
Notes 
Study Plans 
Study Sets 
Find a degree 
Magazine