Biophysics Chapter 2: Equilibrium and Muscles

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Questions and Answers

What happens to a pencil in stable equilibrium when it is displaced slightly?

It returns to its equilibrium position. (correct)

It remains in the same position.

It continues to move further away from equilibrium.

It falls over completely.

Where is the center of gravity located in an erect person?

56% of the person's height from the soles. (correct)

At the top of the head.

60% of the person's height from the soles.

50% of the person's height from the soles.

What can cause permanent distortion of the spine in amputees?

Continuous compensatory bending of the torso. (correct)

Engaging in physical therapy.

Wearing a prosthetic limb.

Balanced weight distribution.

How does carrying an uneven load affect a person's center of gravity?

It causes the body to bend and extend limbs to compensate. Signup and view all the answers

When a pencil's total torque about any pivot is zero, what is its condition?

It is in static equilibrium. Signup and view all the answers

How do people typically adjust their posture when carrying a load to maintain stability?

They bend and extend limbs to shift the center of gravity. Signup and view all the answers

What is the primary measurement unit of force?

Newtons (N) Signup and view all the answers

What is the result of excessive counterclockwise displacement of a pencil in unstable equilibrium?

It increases the displacement. Signup and view all the answers

What happens to torque when the applied force is parallel to the arm?

Torque is zero. Signup and view all the answers

If a person's center of gravity is at 112 cm from the soles, what is their height?

200 cm Signup and view all the answers

How is torque calculated?

Torque equals force times the length of arm. Signup and view all the answers

If a force of 10 N is applied perpendicularly to a lever arm of 2 m, what is the magnitude of the torque?

20 N·m Signup and view all the answers

What does the right-hand rule help determine in the context of torque?

The direction of the torque. Signup and view all the answers

What factor does NOT affect the magnitude of torque?

Mass of the object being rotated. Signup and view all the answers

At which angle is the torque maximized when a force is applied?

90 degrees Signup and view all the answers

What does the term 'normal reaction force' refer to?

The upward force exerted by a surface against an object. Signup and view all the answers

What is the role of the fulcrum in a lever system?

To remain stable while reacting against forces applied to the lever Signup and view all the answers

In a Class 2 lever, where is the load positioned?

Between the fulcrum and the applied force Signup and view all the answers

Which equation correctly relates torque and mechanical advantage in levers?

$Fd_2 = Wd_1$ Signup and view all the answers

What is the mechanical advantage (M) for a Class 3 lever?

M < 1 Signup and view all the answers

What is the significance of the reaction force on the fulcrum?

It serves to stabilize the fulcrum without exerting torque Signup and view all the answers

What is the formula for calculating the anti-clockwise torque produced by the applied force?

Ta = Fa × 1.5 Signup and view all the answers

If the mass of a person is 90 kg and the gravitational acceleration is 10 m/s², what is the weight W of the person?

900 N Signup and view all the answers

What is the restoring torque Tw produced by the weight of a person with mass 70 kg and a distance of 0.1 m?

68.6 N.m Signup and view all the answers

What is the minimum force required to topple a person with a torque of 68.6 N.m at a distance of 1.5 m?

45.7 N Signup and view all the answers

What increases the stability of a person against a toppling force?

Widening the base of support Signup and view all the answers

What is required for a body to be in mechanical equilibrium?

The resultant external force must equal zero. Signup and view all the answers

Which statement best describes stable equilibrium?

The net torque opposes the direction of displacement. Signup and view all the answers

How is the total external force required to topple a person calculated?

By equating Ta and Tw Signup and view all the answers

Which muscles usually end in a single tendon?

Most muscles Signup and view all the answers

Which condition indicates that a body is unstable?

The center of mass is above the base. Signup and view all the answers

What is the role of tendons in the muscular system?

They attach muscles to bones Signup and view all the answers

What happens to forces when a body is in stable equilibrium?

The upward reaction force cancels the downward weight force. Signup and view all the answers

What describes the center of mass of an object?

It represents the average position of all object parts based on mass. Signup and view all the answers

Which scenario aligns with unstable equilibrium?

The body requires a force to maintain its position. Signup and view all the answers

What is a result of having the center of mass outside the base of a body?

The produced torque will likely topple the body. Signup and view all the answers

What does the term 'center of gravity' imply when gravity is uniform?

It coincides with the center of mass. Signup and view all the answers

Study Notes

Biophysics

Biophysics encompasses various fields, including bioenergetics, spectroscopy, Brownian motion, diffusion, bioacoustics, and molecular action.
Other important concepts include entanglement, magnetic imaging, and quantum mechanics.
Key figures in biophysics include Einstein.

Chapter 2: Equilibrium and Muscles

Covers concepts like Force & Torque, Static & Equilibrium, Equilibrium in the Human Body, Muscles and Tendons, Levers, Back muscles, and Elbow.
Illustrations of topics like a rock balanced precariously on a ledge show the importance of calculating and understanding various forces in establishing equilibrium.

Force & Torque

Force and torque are fundamental concepts in physics.
Force is a push or pull that alters an object's state of motion; it is measured in Newtons (N).
Torque is the twisting or turning effect due to a force applied at a distance from an object's rotation axis, measured in Newton meters (N⋅m).
Torque is calculated by multiplying the perpendicular force by the distance from the rotation point to the force application point.
The magnitude of torque is equal to the applied force multiplied by the perpendicular distance to the pivot point.

Static and Equilibrium

A body is static if its linear and angular velocities are zero.
A body is in equilibrium if the resultant external forces and torques are zero.
Stable equilibrium means the body returns to its original position when slightly displaced and is a key concept in physical systems like the human body.

Center of Mass and Stability

The center of mass is the average position of all parts of an object, weighted by their masses.
For a uniform gravitational field, the center of gravity and center of mass coincide.
Stability depends on the position of the center of gravity relative to the base of support. A lower center of gravity enhances stability.

Conditions for Stable Equilibrium

A body is in stable equilibrium if a disturbance produces a restoring force or torque that tends to return the body to its original position.
If the center of mass is above the base of support, the body is typically stable. If the center of mass is below the base, it is unstable.

Static, Stable Equilibrium, and Unstable

Static equilibrium occurs when the net force and torque on an object are zero.
Stable equilibrium occurs when a disturbance causes a restoring force that returns it to its initial position.
Unstable equilibrium is when a disturbance causes a force or torque that moves the object further from its initial position.

Equilibrium in the Human Body

The center of gravity of an upright human with arms at the sides is approximately 56% of their height from the soles of the feet.
The center of mass position changes with posture and body configuration shifts.
Uneven loads cause postural adjustments to maintain balance.

Muscles and Tendons

Skeletal muscle movements are produced by thousands of parallel fibers.
Muscle force depends on the number of contracting fibers.
Tendons attach muscles to bones; most muscles have one tendon, while others, like biceps, have more than one.

Levers

Levers are used to lift loads or transfer movement efficiently.
They consist of a rigid bar that rotates around a fixed point (fulcrum).
There are three classes of levers, distinguished by the relative positions of the load, effort, and fulcrum.
Class 1 levers have the fulcrum between the load and effort.
Class 2 levers have the load between the fulcrum and the effort.
Class 3 levers have the effort between the load and the fulcrum

Elbow

The elbow joint acts as a lever system.
Muscles (like biceps and triceps) work in pairs to flex and extend the forearm.
The force exerted by a muscle depends on the torque generated by the muscle.

Mandible as a Lever

The mandible acts as a class III lever system.
The temporomandibular joint (TMJ) serves as the fulcrum.
The masseter muscle provides the effort to move the lower teeth relative to the bullet.

Back Muscles

Good posture keeps the center of gravity over the feet.
Bad posture often causes back strain because the center of gravity is not over the feet.

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Description

Explore the intersection of biophysics and physics in this quiz, focusing on equilibrium concepts and muscle functionality. Key topics include force, torque, and their applications in the human body, illustrated through practical examples. Perfect for those interested in understanding the mechanics of muscles and equilibrium.