Palmer Biomechanics Module 1

Front 1

What is meant by a scalar?

Back 1

A quantity that has only magnitude - no direction, such as temperature.

Front 2

What is meant by a vector?

Back 2

A quantity that has both a magnitude and a direction, such as velocity or force.

Front 3

What is the difference between speed and velocity?

Back 3

Speed (a scalar) refers to only the magnitude component of velocity (a vector) - how fast you are going without any reference to what direction you are moving in.

Front 4

What is the defining characteristic of a Cartesian coordinate system?

Back 4

These axes are perpendicular (orthogonal) to each other.

Front 5

What is a unit vector?

Back 5

A vector of unit length (that is, 1 in whatever units you are using) in the direction of one of the axes of a Cartesian coordinate system.

Front 6

What name is usually used for a unit vector along the X axis of a Cartesian coordinate system? along the Y axis?

Back 6

i is along the positive X axis_
j is along the positive Y axis

Front 7

What is the "normal" component of a vector?

Back 7

The component that is perpendicular to the relevant surface.

Front 8

What is the name of the component of a vector that is parallel to the relevant surface?

Back 8

tangential

Front 9

What is meant by the hypotenuse of a right triangle?

Back 9

The long side of a triangle that contains a 90 degree angle.

Front 10

What is the Pythagorean Theorem?

Back 10

The sum of the squares of the sides of a right triangle is equal to the square of the hypotenuse.

Front 11

If vector A = 5i - 4j and B = 2i + 6j, what is the sum of A + B?

Back 11

7i + 2j (add the i components and then add the j components)

Front 12

If vector A is 3i - j, what is the vector 4A?

Back 12

4(3i - j) = 12i - 4j (multiply the i coefficient by 4, and then the i coefficiant)

Front 13

What kind of coordinate system is good for describing rotary movements?

Back 13

polar coordinate system

Front 14

What is it that a moment quantifies?

Back 14

the tendency of a force to cause rotation about an axis (pivot point)

Front 15

When referring to moments (torques), how is the moment arm defined?

Back 15

the shortest (perpendicular) distance from the line of the force to the pivot point.

Front 16

What kind of coordinate system is good for describing rotary movements?

Back 16

polar coordinate system

Front 17

How is the magnitude of a moment calculated?

Back 17

the magnitude of the force times the moment arm

Front 18

How is the "direction" or sense of a moment determined?

Back 18

The right hand rule. Curl the fingers of the right hand around the pivot point with the fingers pointing in the direction of the rotation that would be caused by the moment. The sense of the moment is given by the direction of the thumb._
(usually express as 'into the paper' for clockwise or 'out of the paper' for counterclockwise)

Front 19

If a force is directed at the center of gravity of a rigid object, what type of movement will it tend to cause?

Back 19

translational (in a straignt line - not rotational)

Front 20

If a body is rigid, in what simplified way can you think of the distribution of its mass?

Back 20

as being concentrated at the center of gravity

Front 21

What are the two conditions of static equilibrium?

Back 21

1. the sum of forces = 0_
2. the sum of moments = 0

Front 22

What is a force couple?

Back 22

a pair of equal but opposite forces offset equally from the center of rotation_
(like hands on a steering wheel)

Front 23

What type of movement does a force couple tend to cause?

Back 23

rotation (not translation)

Front 24

What is Newton's First Law of Motion?

Back 24

a particle will move at a constant velocity unless acted upon

Front 25

What is Newton's Second Law of Motion?

Back 25

F = ma (the net force required to cause acceleration of a rigid body it determined by the product of the mass of the body and on how fast you want it to accelerate)

Front 26

What is Newton's Third Law of Motion?

Back 26

For every action there is an equal and opposite reaction

Front 27

If there is an equal but opposite reaction for every force, why don't the two cancel out resulting in no motion?

Back 27

the action and reaction are on different bodies

Front 28

What kind of objects do Newton's Laws of Motion apply to?

Back 28

particles - all mass concentrated at one point with no volume_
(can often think of a rigid body as a particle if it is uninhibited)

Front 29

In what kind of situation do Newton's Laws of Motion apply?

Back 29

inertial reference system (that is, when you are either stationary or moving in a straight line at a constant speed)

Front 30

What is the basis for Newton's Laws of Motion?

Back 30

they are empirical - based solely on observation with no theoretical basis

Front 31

What type of system analysis involves only a description of motion - nothing about the forces required to cause that motion?

Back 31

kinematics

Front 32

What type of system analysis includes calculation of the forces involved?

Back 32

kinetics

Front 33

How is work defined?

Back 33

force times the distance an object is moved as a result of that force

Front 34

How is the potential energy of an elevated weight defined?

Back 34

the weight of the object times the height to which it is elevated

Front 35

How is power defined?

Back 35

power = work / time

Front 36

How is impulse defined?

Back 36

force times the length of time that force was applied

Front 37

How is stress defined?

Back 37

force per unit area

Front 38

What kind of load causes an avulsion fracture?

Back 38

tensile load

Front 39

When applying a load to an object, how is strain defined?

Back 39

change in length divided by the original length

Front 40

When generating a plot, what is the independent variable?

Back 40

The variable that is controlled as part of an experimental protocol.
It is usually plotted along the x (horizontal) axis.

Front 41

When generating a plot, what is the dependent variable?

Back 41

The variable that is measured during the course of an experimental protocol._
It is usually plotted along the y (vertical) axis.

Front 42

When referring to a stress/strain plot, how is Young's modulus of elasticity, or stiffness, defined?

Back 42

The slope of the plot in the elastic (linear) region.
This is often expressed as "rise over run".

Front 43

When referring to a specific solid material, what does isotropic mean?

Back 43

That it behaves the same in every direction.
(unlike wood or bone - which are anisotropic)

Front 44

When referring to bending an object, what is meant by the neutral axis?

Back 44

The region within the object that has neither compressive or tensile stress

Front 45

What are the two basic varieties of bending?

Back 45

3 point and 4 point

Front 46

Where is fracture most likely to occur in 3 point bending?

Back 46

opposite the middle point

Front 47

Where is fracture most likely to occur in 4 point bending?

Back 47

at a point of weakness in the region opposite the 2 middle points

Front 48

What kind of loading tends to cause sliding or angular distortion?

Back 48

shear

Front 49

What kind of loading besides bending also has a neutral axis?

Back 49

torsional

Front 50

What kind of fracture results from torsional loading?

Back 50

spiral fracture

Front 51

What class of lever has the applied force between the fulcrum and resistance?

Back 51

3rd class

Front 52

What class of lever has the fulcrum between the applied force and resistance?

Back 52

1st class

Front 53

How is the mechanical advantage of a lever defined?

Back 53

the moment arm of the applied force divided by that of the resistance

Front 54

What class of lever always has a mechanical advantage greater that 1?

Back 54

2nd class

Front 55

What class of lever can have a mechanical advantage that can be either less than, equal to, or greater than 1?

Back 55

1st class