BIOMECHANICS OF HUMAN MOVEMENT

Question 1

Define Colinear ( one-dimensional ) in a force system

Answer 1

this is when the forces are acting in the same plane and along the same line of action. They point in either the same or opposite directions. This is shown in

Question 2

Buoyancy

Answer 2

Is the upwards force that the fluid exerts on a body immersed in water

Archimedes’ principle: every body immersed in water will experience an upwards force proportional to the weight of fluid displaced.

The buoyancy force acts on the COG of the displaced fluid and is Center of Buoyancy. (not necessary the cog of the body immersed in water.)

Question 3

What does it mean If the distance of the force arm to the axis is greater the distance of the load arm from the axis?

Answer 3

Movement is easier to occur, therefore, The system is said to have mechanical advantage. Which means less force is needed to create movement

Question 4

How could we use principles of hydrostatic pressure and buoyancy in rehab settings to faciliate movement?

Answer 4

We could use it to increase muscle work and balance

We could use the principle of buoyance to facilate passive movement and to help with balance.

Use the principle of flow to train strength and balance.

Question 5

How do you calculate the strain of linear tension and compression versus something like a shear strain acting on a material?

Answer 5

Strain of linear tension and compression = New length - the original lenght divided by original length

Shear strain/ angular deformation = divide the displacement of the object from the height.

d/ h

Question 6

Define mechanical energy, energy and work and explain the relationship between the three

Answer 6

In review, mechanical energy is energy possessed by an object due to its motion or its position. Energy is the ability to do work, and work is accomplished when a force moves an object. Mechanical energy comes in two forms: kinetic energy, in which an object has the ability to do work when it moves, and potential energy, in which an object has the ability to do work due to its position. In either case, mechanical energy is the ability to do work.

Question 7

Define Hydrostatic pressure

Answer 7

is the pressure exerted by a fluid and acts in all directions and with increased depth, there is increased pressure.

Question 8

Define Acceleration

Answer 8

Acceleration is defined as the rate of change of velocity and is described in metres per second squared (m/s 2 ).

Acceleration is zero = constant speed

If the car maintain its speed n the highway, it’s acceleration is zero. But if it slows down 5km and speed ups 5 km. It’s acceleration is 5 km

a = vf - vi

Accelleration = change in speed 60 km - 30km

Question 9

Describe the 3 types of linear stress that could deform a material

Answer 9

Linear strain: the loads are acting along the same line of action but in opposite direction. The resulting deformation is lengthening and some narrowing Eg., an elastic band being pulled apart.

Linear compression: when two equal loads are acting along the same line of action, toward each other . Eg..,, squeezing. The resultant deformation will shorten with some widening

Shear stress: when two parallel and equal loads are applied inopposite directions but not on the same line of action. (no change in length but an angular deformation)

Question 10

Stability Limit

Where is the Center of pressure?

Answer 10

An area within the base of support when COG an be shifted around wiwth minimal effort of maintaining balance.

During quiet standing, COP lies within stability limit.

Question 11

What is Elasticity?

Answer 11

is the property of material which allows it to return to its original shape or length after being distorted (Eg. Glass will break, others will bend when stretched)

-

Question 12

Law of acceleration

Answer 12

The rate of change of momentum of a body is proportional to the applied force and takes place in the direction in which the force acts.

A body or object would stay at rest or at a constant motion in a straight line and will continue to do so, until an external force is apply to increase its speed.

Force = mass x acceleration

N = kg.m/s^2

Question 13

What is buoyant force caused by? What causes this?

Answer 13

The buoyant force is caused by the hydrostatic pressure, or the pressure caused by the displaced fluid, wanting to return to where it was before it was displaced

Question 14

Where would be the application of the force by the biceps muscle be located?

Answer 14

At the insertion point of the biceps brachii

Question 15

What is kinetic and potential (gravitational) energy and what are they dependent on?

Answer 15

Two main types of energy on earth, Kinetic energy, Potential energy

What is kinetic energy and what is it depend on? Every object is capable of motion. Desk, walls, … atoms that make up these objects. Motion exist in every atoms, and atoms orbit a nucleus, so motion exist in every object. Motion is in every molecule. Motion is kinetic energy. Kinetic energy is energy in motion. Every cell has moving parts.

Kinetic energy is dependent on speed and mass. Ek = 1/2 x velocity The faster the object travel. But also, the larger the mass, and the faster it is going = more kinetic energy.

Every object has potential energy stored in it and it becomes kinetic energy at a particular height when dropped. … the higher the object is to the ground, the more potential energy it could store. Once you jump from a tall building, you become kinetic energy. Potential energy is depenedent on the position in a gravitation field .. the higher you Ep=mass x gravity x height

Question 16

Define Lever

Answer 16

defined as a rigid bar that rotates around a fixed point or fulcrum.

Question 17

A person with mass of 75kg is standing on the floor. What is the magnitude of the ground reaction force?

Select one:

a. 225N
b. 150N
c. 750N
d. 75N

Answer 17

c. 750N

Question 18

Which statement about mechanical advantage is correct?

Select one:

a. A system in mechanical advantage will require more force to create the same amount of angular displacement than a system in mechanical disadvantage
b. A system in mechanical advantage means that a smaller force will create movement
c. A system in mechanical advantage will require greater muscle activation to create movement
d. A system in mechanical advantage means that the distance of the load (resistance) from the axis of rotation is greater than the distance of the force from the axis of rotation

Answer 18

b. A system in mechanical advantage means that a smaller force will create movement

Question 19

Define Moment or Torque

An example of a torque

Answer 19

Moment is the movement of turning resulting from a force

Torque is the twisting movement resulting from a force

The biceps brachii produces a torque that causes the elbow to bend (elbow flexion)

On the other hand, the barbell is also creating a torque downwards

Question 20

True or false

A body that is less stiff will tend to deform more and produce greater elastic energy.

Answer 20

True

Question 21

Which statement about mechanical advantage is correct? Select one:

a. A system in mechanical advantage will require more force to create the same amount of angular displacement than a system in mechanical disadvantage
b. A system in mechanical advantage means that a smaller force will create movement
c. A system in mechanical advantage will require greater muscle activation to create movement
d. A system in mechanical advantage means that the distance of the load (resistance) from the axis of rotation is greater than the distance of the force from the axis of rotation

Answer 21

B. less force is required.

Question 22

What is biomechanics?

Answer 22

Biomechanics can be defined as the study of the structure and function of biological systems, such as the human musculoskeletal system, by application of (Newtonian) mechanics.

Question 23

What is Flow and how could it affect movement in water?

Laminar and Tuberlant Flow

Answer 23

Flow: the movement of the liquid from one point to the other (usually due to pressure difference) The flow of water is influence by the speed and direction of the water

Laminar flow: is the smooth movement of a liquid…the molecules of laminar flow are organized into “layers” or “laminae.” The water move in a streamlined way-slowly and linearly. (Low velocity: slow speed, in one direction)

Turbulent flow: irregular pattern of the movement of the fluid due to some sort of disturbance to the liquid. Since the water moves in random directions, and usually at a higher velocity, this type of flow will cause more resistance to the movement of the body than a laminar flow.

Question 24

What does it mean to have an mechanical advantage of greater than 1?

Answer 24

1. It makes lifting easier.
2. The force arm is greater than the load arm

Question 25

Define Inertia versus Moment of inertia

Answer 25

The tendency of an object to resist changes in motion

The tendency of an object to resist angular changes in motion

Question 26

Define Angular velocity (ω) and Angular acceleration (α)

What are the units of measurement?

Answer 26

Angular velocity (ω) is defined as the rate of change of angular displacement. It is measured in degrees per second or radians per second.

(degrees/s or rad/s)

Angular acceleration (α) is the rate of change of angular velocity and is expressed in degrees per second squared (°/s ^ 2 ) or radians per second squared (rad/s^2)

Question 27

Exercising in water is different from exercising on land. During the aquatic exercise below, which muscle is mostly active concentrically?

a. Hip abductors when the leg is coming down
b. Hip adductors when the leg is going up
c. Hip adductors when the leg is coming down
d. Hip abductors when the leg is going up

Answer 27

Answer: Hip adductors when the leg is coming down. This question follows the same principle as the question on the case study. Because you have buoyancy acting upwards, it assists the movement of hip abduction.

Therefore, the muscles most active concentrically are the hip adductors when the leg is coming down (resisting the force of buoyancy).

Question 28

How do you calculate potential (gravitational) energy?

Answer 28

Potential energy is equal to the mass X gravity x height,

gravity is the acceleration due to gravity

height is the position of the body above the baseline

Question 29

The image below represents a 2-dimensional force system. What is this system called?

Select one:

a. Orthogonalcross out
b. Coplanarcross out
c. Concurrentcross out
d. Parallel

Answer 29

b. Coplanarcross out

Question 30

What determines whether the object floats in water or not?

Answer 30

1. Density of the liquid, or how much mass there is per unit area.
2. Volume of the fluid displaced by the object
3. Weight of the object

If a light object can displaced a lot of fluid, it would have a lot of buoyant force, so it would float.

Question 31

In order to be able to cross a street safely, a person needs to be able to walk at a speed of at least 1.2 m/s. Jane is able to walk 500 meters in 20 minutes. Based on this information, which statement below is correct?

Select one:

a. Jane’s walking speed is equal to 1.2 m/s
b. It is not possible to determine Jane’s walking speed with this informationcross out
c. Jane is safe to cross the street because her walking speed is greater than 1.2 m/s
d. Jane is unsafe to cross the street because her walking speed is less than 1.2 m/s

Answer 31

d. Jane is unsafe to cross the street because her walking speed is less than 1.2 m/s

Question 32

State Hooke’s Law and its equation

Answer 32

States that the force needed to compress or extend a spring is directly proportional to the distance you stretch it. So the more you stretch something that harder it is to keep stretching it (Linear relationship).

In other words, for every incremental unit of stress, there is a corresponding incremental increase in strain. When you stretch a material there is a “restoring force” that restore the material being stretched.

• Elastic Energy is equal to one-half the stiffness of the material multiply by the change in length squared. Es = 1/2Kx^2

k = spring constant

x = to the change in length of the material from original to stretched

Question 33

Orthogonal forces vs Concurrent forces

Answer 33

Orthogonal forces: The directions of the forces are perpendicular to each other

Concurrent forces : two or more forces originate from the same point of application, or their lines of action intersect at a common point (before they impact on the body)

Question 34

You are performing gastrocnemius (ankle plantarflexor muscle) stretch to a patient as shown in the image below. What is the direction of the elastic force of the gastrocnemius muscle?

Select one:

a. Straight up, in the opposite direction of gravitycross out
b. Towards dorsiflexioncross out
c. Towards plantarflexioncross out
d. Straight down, in the same direction as gravity

Answer 34

c. Towards plantarflexioncross out

The stretch shown is toward dorsiflexion. The elastic force would tend to bring the muscle to its original shape, therefore toward plantarflexion.

Question 35

If a person starts with the arm down by the side and performs full ROM of shoulder abduction (end position shown in picture on left), then performs shoulder adduction to 90 degrees (end position shown in picture on the right). What is the total angular displacement of the arm?

Answer 35

90 degrees

Question 36

What is the buoyant force?

Describe the archimedes’ principle

Answer 36

Is the upward force that an underwater object feels

Buoyant Force is the upward force of a fluid that allows you to be light and play around in the water in a way that you can’t do on land. This buoyancy force could happen due to the the pressure being exerted greater at the bottom…near your legs. So if you lift your leg up, the pressure of the water acts up on your thigh, bringing it upwards. If you tilt back or forward, the buoyant force will act to rotate you. Because the forces on the bottom, near the bottom of the body of the water, it creates a net upward force, so the body is buoyed up against gravity.

To put a number on the buoyant force, we use the archimedes’ principle which states that the buoyant force of a submerged object is equal to the weight of the liquid displaced by the object.

(eg. Each time you put an object in water, the object is displacing the water that would be there if you hadn’t put it in water)

Question 37

Parallel forces

Answer 37

the directions of the forces are parallel in the same or opposite directions.

Parallel forces in opposite directions may produce a force couple, as in a steering wheel.

Question 38

Which statement best describes potential energy?

Select one:

a. Every object that has a mass will have potential energycross out
b. Every object in movement will have potential energycross out
c. Every object suffering the influence of gravity will have potential energycross out
d. Every object that is influenced by gravity and is not resting on a surface will have potential energy

Answer 38

d. Every object that is influenced by gravity and is not resting on a surface will have potential energy

Question 39

Define Center of Gravity, Center of Mass, Line of Gravity

Answer 39

The center of a body where all the weight is considered to be concentrated.

Center of mass is the point about which the mas of the object is evenly distributed

Line of gravity is the projection of the center of gravity to the ground.

Question 40

Despite requiring a greater force to overcome the resistance of grade 3 levers, this type of lever has what type of advantage?

Answer 40

Speed advantange, once the force is generated to overcome the resistance, this load end of the lever will move at a greater velocity than the point to which the force is applied.

Example, the force of the biceps muscle will cause greater angular displacement & speed distally

Question 41

Based on the image below, answer the following questions:

1-What is the direction of the moment that the line of gravity is creating at the head: towards flexion or towards extension?

2-Which muscles are most active to maintain the head in this position: neck flexors or neck extensors?

Answer 41

toward neck flexion

neck extensors

Question 42

What is pressure/stress?

What is the center of pressure?

Answer 42

The pressure is the force applied to a surface area.

Pressure can be defined as the force per unit area (in m^2) or

Pressure = F/ A

Pa = N/M^2

Eg., Too much pressure/force on one area when sleeping could create sore spots.

The center of pressure (COP) is the point of GRF application and is colinear with COG during standing

It can be seen from the equation above that if a force remains the same and the surface area increases, then the pressure exerted by the force will be less. Conversely, if the surface area is decreased while the force remains the same, greater pressure will be felt from the force. This is important when considering the pressure felt on the human body when lying in a bed. If the force is being channelled through a small surface area, such as a bony point, then the pressure over that area will be much greater than if the force from the body were acting on a large surface area. In the latter case, pressure sores would be less likely to occur.

Question 43

State the Principles of energy conservation

Answer 43

• the sum of energy is assumed to always be constant
• one form of energy can be transformed into another
• energy is not created or destroyed

Question 44

HOw is muscle force calculated?

This could result in a positive (concentric) or negative (eccentric) work.

During an eccentric contraction the muscle force and the change in the muscle length are in the ______ ______

Answer 44

Muscle Work

= muscle force (N)

x

change in muscle length

(the distance between the muscle origin and insertion) (eg. maybe .05m)

opposite direction

Work = Force x distance

Question 46

How do you calculate the moment of force?

Answer 46

Moment (M) = force (F) x moment arm (d)

The moment can be calcuated by multiplying the force acting on the system, by the distances of the application of the force, which is caused the moment arm.

The biceps muscles need to produce a force on the bone to counteract the force produces by the load. The distances of insertion from the bicep to the axis of rotation is the moment arm of the biceps.

The weight produces a moment at the system.

Question 47

Which of the following statements best describes hydrostatic pressure?

Select one:

a. The upwards force that a fluid exerts in a body immersed in water
b. The mass of fluid divided by its volume
c. The force that a fluid exerts in all directions
d. The movement of fluid from one point to another

Answer 47

c. The force that a fluid exerts in all directions

Question 48

Due to its intrinsic properties, a muscle can deform and, therefore, produce elastic force. Which one of the following statements best describes this?

Select one:

a. A muscle will deform (stretch) in the opposite direction of the force applied to it
b. The more a muscle deforms, the smaller the elastic force it will generates
c. The amount of elastic force a muscle generates is proportional to its weight
d. A muscle will deform (stretch) more depending on the magnitude of the force applied to it

Question 49

Define Moment of Inertia (newton’s 1st law)

How do you calculate it?

Answer 49

Inertia (I) is the tendency of an object to resist changes in its angular motion.

moment of inertia is equal to the mass of an object multiply by the distance of the mass from the axis of rotation.

I= m x r ^2

Question 50

Describe the concept of linear and angular movement

Answer 50

Linear motion:

If the direction of a force is parallel to the movement and applied to the COG or COM, the resultant force would either be a increased or decreased in acceleration.

Distance = displacement

Angular motion:

If the direction of force is not parallel to the movement and being applied above or below (anywhere but the center of COM, the object will rotate.

Linear and angular combined movements:

The direction of force while is parallel to the movement is applied not at the COM, a unpredictable random resultant

Example: In running, there is an angular rotation at the knee joint but the hip joint is moving curvilinearly.

Question 51

How do you calculate the moment of buoyancy?

Answer 51

Moment COB = ForceCOB x distance to the axis of rotation

Question 52

Hydrostatics vs Hydrodynamics

Describe concept of hydrodynamic pressure

Answer 52

Here are two concept of mechanical principles of fluids.

Hydrostatics is the study of the effects of force and pressure on a fluid at rest. 3 states of fluid/water: solid (ice), gaseous (above 100 deg, steam), or water. Water itself has a variety of forces acting on it. And forces that acts on it makes the water move in various ways.

Hydrodynamics is the study of the effects of force and pressure on a fluid in motion. Pressure is the applied force on a fluid that is contained.

Pressure in a fluid acts at a point/small surface. We feel this pressure when we are in a swimming pool. We feel more pressure when we are in the deep end and we are diving deeper and deeper. The pressure we feel is acting on us from all angles.

Pascal’s Law: states that this force is equal in all directions and is independent of gravity. Pressure within the fluid is also the result of the weight of the fluid above. P = vertical distance from the point to the surface multiply by the weight density of the fluid. So the deeper you swim in the ocean, more fluid is piled ontop of you, the more pressure you would feel.

Pressure = depth x depth and density of water

Fluid weight Density = fluid mass x acceleration due to gravity/ volume

Question 53

Two force vectors are acting parallel to each other and in the same direction. One has the magnitude of 20N and the other 35N. What is the magnitude of the resultant?

Select one:

a. 55N

cross out

b. -15N

cross out

c. 65N

cross out

d. 15N

Answer 53

55 N?

Question 54

Why is it important to understand mechanical advantage?

Answer 54

Because it could make movement easier or harder to occur.

Question 55

How do you Calculate Power?

Rotational power?

muscle power?

Answer 55

Power = F x V

Rotational Power = moment x angular displacement/t

muscle power = force x velocity of contraction

Question 56

HOw do you calculate mechanical advantage?

Answer 56

MA = force arm/ load arm

Mechanical Advantage is calculated by dividing the distance fro the axis to the force (dforce) by the distance from the axis to the load (dload).

MA = 1

MA > 1

MA < 1

Question 57

Define centripetal force

Answer 57

makes body move in a circular motion and the line of force application is orthogonal (perpendicular) to the velocity of body

Centripetal force As stated earlier, a body or object that is moving at a constant speed in a straight line will continue have to be applied to make the object change direction continuously. This force is called a centripetal force. In the hammer throw, this centripetal force is produced by the thrower. The thrower will, however, perceive himself as being pulled by the hammer, which is often called the centrifugal force. In a biomechanical analysis, it is better to consider the centripetal force only. As soon as the thrower lets go of the hammer, it continues moving in a straight line because the centripetal force is no longer operating.

Question 58

If the forces for buoyancy and COG is not colinear, what would happen to the object?

Answer 58

The object would rotate until the COB and COG coincide

Question 59

ductility

Answer 59

is the amount of stress a materal can handle before it fails.

Question 60

What is energy? Describe the three types of energy?

Answer 60

The capacity of a force to produce work.

1. potential: the energy an object has in relation to its position in a gravitational field, if gravity = 0, then the object does not have Ep
2. kinetic: the energy a body or object has by being in motion. It is proportional to the object’s mass and speed of movement.
3. elastic: the energy a body has after being deformed from its original shape
4. metabolic: energy obtained by the body from food, which is necessary to maintain the basic metabolic function, including muscle contraction (ATP needs to be present in the muscle)

Question 61

You are performing gastrocnemius stretch to a patient as shown in the image below. What is the direction of the elastic force of the gastrocnemius muscle?

Select one:

a. Straight up, in the opposite direction of gravity
b. Towards dorsiflexion
c. Towards plantarflexion
d. Straight down, in the same direction as gravity

Question 62

What does Hooke law offers?

Answer 62

Hooke’s law gives us the force we need to find elastic potential energy. Looking at a graph of force versus displacement, we can find that the formula for elastic potential energy is PE = 1/2(kx^2).

Question 63

How do these concepts apply to the human body?

Answer 63

Force are acting on the human body at all times. Those are external or internal forces and they produce moment or torque on the body parts. Depending on the moment arm, lever or axis of rotation muscles will work differently. This can lead to mechanical advantage or disadvantage of human movement.

Question 64

Which system below has the greatest mechanical advantage?

F=Force, R=Resistance

Answer 64

Select one:

a. I
b. I and III
c. III
d. II

Question 65

Describe Stability vs Balance

What are the 4 criterias of stability?

Answer 65

Balance: The object or body is in a state of Balance when the COG falls within the BOS.

Stability: is the ability of an object to maintain its balance after being disturbed.

Stability is dependent on:

1. The surface area of the BOS
2. the location of the LOG above the BOS . (staying within the limit area)
3. the height of the COG above the BOS
4. the mass of the body

Question 66

What is the difference between type 2 and type 3 levers?

Answer 66

c. Type 2 levers the resistance is between the axis of rotation and the force and type 3 lever the force is between the axis of rotation and the resistance

Question 67

State Pascal’s Law

Answer 67

Pascal’s principle states that a change in pressure at any point in an enclosed fluid will be transmitted undiminished to all parts of that fluid.

A fluid is defined as any substance that flows and that takes the shape of its container.

Because the fluid cannot be compressed, the pressure remains constant throughout it. Pressure is the force exerted over a given area.

Question 68

A person swims 10 laps of a 50 m pool (one lap = one length of the pool) in 15 minutes. What is the total distance that the person swims?

Select one:

a. 5000 m
b. 500 m
c. 2500 m
d. 250 m

What was his swimming speed?

Answer 68

1 lap = 25 m

10 laps x 25 m =

Total Distance swam = 250 m

Swimming speed = V = d/t

V = 250 m / (60x15)

= 0.28 m/s

Question 69

Why is it important to know the centre of buoyancy in an object?

Answer 69

Knowing where the center of buoyancy is located is vital to know for the stability of an object floating in a fluid. When a boat, for example, is floating in the water, the object’s weight and the buoyant force exerting on the boat are equal, and those forces are acting through the center of buoyancy and the center of mass. If those two points are close to each other, then the rocking the boat experiences will be minimized. On the other hand, if the two points are far apart, then the rocking will increase and the risk of the boat capsizing increases.

Question 70

Name two effects of inertia on human body

Answer 70

1. It is harder to move a body part that has increased mass
2. It is harder to move a body part that (has its COM) farther away from the axis of rotation

Eg., hip flexion with knee extension vs flexion

Question 71

What are the 3 components of force?

Answer 71

1. Magnitude : the longer the arrow, the greater the magnitude.
2. Direction or line of action : the arrow points in the direction of the force.
3. Point of application : the point of the arrow is located at the point of application.

Question 72

If the line of gravity is within the base of support, then the body is said to be in ____

Answer 72

balance

Question 73

What determines stability in water?

Answer 73

The relationship between the COG and the COB will determine stability

Question 74

Define Strain

Answer 74

Strain = change in dimension divided by its original dimension

the measure of deformation undergone by the object due to the stress that has been placed on it is termed the strain;

Question 75

What is the direction of the ground reaction force on the knee of a person performing leg press exercise, as in the image below?

Select one:

a. Diagonally up and to the rightcross out
b. Downwards (parallel to the line of gravity)cross out
c. Upwards (parallel to the line of gravity)cross out
d. Diagonally down and to the leftcross out

Answer 75

d. Diagonally down and to the left

Diagonally down and to the left. In this question you should be looking at the force that the platform is exerting on the knee, therefore it is diagonally down and to the left (opposite to the force that the person is exerting on the platform

Question 76

What is elastic energy in the human body?

Answer 76

• The energy a body has after being deformed from its original shape.

Question 77

How do you calculate linear kinetic energy?

Answer 77

Linear kinetic energy is equal to half the mass x velocity squared

Ek = 1/2 m X v^2

Question 78

Define friction. Static vs dynamic friction.

If a force is applied to an object that does not move over a surface, then there must be a _______ force that is _____________

Answer 78

It is the resisting force that is felt between two objects when they are moved against each other, eg., foot and ground. the direction of motion is always opposite to its force

frictional force that is equal and opposite to the applied force. Static friction: between 2 bodies at rest. Dynamic friction: between moving bodies

application of force –> A critical value of friction is reached before movement occurs

The coefficient of friction is mu and is dependent upon the state of the object, surface condition, type & direction of applied force

Useful? allowed for controlled movement to take place. or they could be hindrance as they require energy to overcome as in some type of exercise.

Question 79

What is the Spring Constant

What is the constant depended upon?

Answer 79

a number that represents how much force it takes to stretch a lateral - materials with larger spring constants are stiffer. (It other words, it is the measure of the stiffness of a spring)

Question 80

Describe the concepts of motion (linear and angular).

Answer 80

Force and moment can lead to movement (motion)

Linear motion occurs when an object travels in a straight line or does not follow a straight path. Like running around a track.

Question 81

What is center of buoyancy?

Answer 81

The center of buoyancy is the point where if you were to take all of the displaced fluid and hold it by that point it would remain perfectly balanced, assuming you could hold a fluid in a fixed shape. This point is also called the center of mass. The center of buoyancy for an object is the center of mass for the fluid it displaces.

Question 82

Law of acceleration

Answer 82

• The change of momentum of the body is proportional to the force applied and

will occur in the same direction of the force

Question 83

If in a lever system, the resistance lies between the fulcrum and the force. What type of lever is this? Give an example.

Answer 83

Second order lever. This lever is helpful for lifting a load, as in a crowbar or wheelbarrow.

Ex. on human body: Going on the toe by raising the body up. The ball of the foot is the axis of rotation, the ankle plantarflexor muscles are the force, (insertion of the gastroc muscle at the calcaneus) and the resistance is the weight of the body acting in front of the ankle, bringing down the heel.

Question 84

What are coplaner forces? Give examples

Answer 84

The forces are acting on different lines of action, but is acting on the same plane.

Eg., Arrow is pointed south and another Arrow is pointed east

The car is being pushed from all direction. Not a very efficient way to move the car in a straight line.

Question 85

What is elastic potential energy?

Answer 85

This is the energy an object has in it due to being deformed. Any object that can be deformed and then return to its original shape can have elastic potential energy. Eg., muscles, cartilages, ligaments,

When you deform these objects, they move back to their original shape on their own.

As a counter-example, an object that would not be affected by elastic potential energy would be bone.

Question 86

What would occur to the body that is in water with a density greater than 1 ? Body with density < 1

What is Human body density?

Answer 86

will sink

will float

varies: 0.86-0.97