2 Mechanics of the Body Free Online FlashCards

What does biomechanics study?

Biomechanics applies mechanics to living bodies, studying how forces produce movement and how loads are carried by tissues and devices.

What is a force, and how is it measured?

A force is a push or pull with magnitude and direction, measured in newtons (N).

State Newton’s second law.

Newton’s second law is $\sum \vec{F}=m\vec{a}$: net force equals mass times acceleration.

What happens when the net force on a body is zero?

The body has no linear acceleration; it remains at rest or moves at constant velocity.

What does a free-body diagram show?

A free-body diagram isolates an object and shows all forces acting on it.

What is torque, and how is it calculated?

Torque is a force’s turning effect about a pivot: $\tau=rF\sin\theta=r_{\perp}F$.

How can a force produce more torque about a joint?

A force applied farther from a joint, or more nearly perpendicular to the limb, generally produces greater torque.

What roles do bones, joints, and muscles play in a body lever?

Bones act as levers, joints as pivots, and muscles provide the applied forces.

What torque does a 20 N object produce 0.30 m from the elbow?

The object produces $20\times0.30=6.0$ N·m of torque about the elbow.

What muscle force balances 6.0 N·m with a 0.04 m lever arm?

Ignoring other forces, the muscle must exert about $6.0/0.04=150$ N to balance the object’s torque.

What is stress, and how is it calculated?

Stress is force distributed over an area: $\text{stress}=F/A$. It is measured in pascals $Pa$.

What is strain, and how is it calculated?

Strain is relative deformation: $\text{strain}=\Delta L/L_0$. It is dimensionless.