EXAM

Question 1

what does coefficient of friction represent ?

Answer 1

A measure of the amount of friction existing between two surfaces.

Question 2

Instantaneous Velocity

Answer 2

-a continuous function of time and gives the velocity at any point in time during a particles motion.

-Velocity of an object under the motion in a point of time

Question 3

Acceleration

Answer 3

is the rate the change of the velocity of an object with respect to time
-allows you to measure how fast velocity changes in meters per second squared

Question 4

Tangent Line of a Curve

Answer 4

-a straight line that “just touches” the curve at that point

-the slope of the tangent line is then a distance travelled divided by an elapsed time and can thus be interpreted as a velocity.

Question 5

displacement

Answer 5

the shift in location when a object in motion changes from one position to another

Question 6

Visual estimation of velocity

Answer 6

Forward direction is Positive
Backward direction is negative

Question 7

visual estimation of acceleration

Answer 7

Acceleration is independent of the direction of motion. Both positive and Negative accelerations can result without the object changing direction.

Question 8

Shuttle Run Position-Velocity-Acceleration
SAME SIGN:

Answer 8

-acceleration is positive when accelerating (increasing speed)
-acceleration is negative when decelerating (decreasing speed)

-Velocity is positive when going in one direction
-Velocity is negative when going in opposite direction.

Question 9

Shuttle Run Position-Velocity-Acceleration
VELOCITY IS ZERO

Answer 9

-velocity is zero because the runner is switching direction

Question 10

Shuttle Run Position-Velocity-Acceleration
ACCELERATION IS ZERO

Answer 10

-is zero when speed is constant
-when runner/person is neither decelerating or accelerating.

Question 11

Relative Joint Angle

Answer 11

-is the angle between two longitudal axes of two segments
-this will not describe the position of the segment in space
-three points of interest needed; proximal, vertex, and distal points

Question 12

Absolute Angles

Answer 12

-the angles of inclination of a body segment relative to some fixed reference in the environment
-Two points of interest: proximal and distal

Question 13

Segment Angle

Answer 13

The angles calculated relative to right horizontal is called segment angle

Question 14

Angular Motion

Answer 14

measured relative angle is compared to angle of joint in the anatomical position

Hip Angular motion: 180-relative angle of hip
Knee Angular motion: 180-relative angle of knee
Ankle Angular motion: 90-relative angle of ankle

Question 15

Gait

Answer 15

Purpose: to get from one point to the next major motor functions

1. Maintenance support of the upper body
2. Maintenance of an upright posture and balance of the HAT head, arm, trunk
3. Control of foot trajectory for ground clearance and gentle heel/toe landing
4. Generation of mechanical energy to maintain velocity
5. Absorption of mechanical energy for shock absorption and stability or to decrease velocity

Question 16

Single Support Phase

Answer 16

is also known as the swing phase where only one limb is in contact with the ground
-occurs between the heel strike of one foot and the toe off of the opposite foot.

Question 17

Double Support Phase

Answer 17

Portion of walking cycle when both feet are in contact with the ground simultaneously
-occurs twice during each gait cycle, once when the first foot makes contact with the ground (heel strike) and the second foot begins to make contact, AND again when first foot Is lifting off the ground (toe off) and the second foot remains in contact.

Question 18

Gait Parameters - Stride Length

Answer 18

distance between successive points of initial contact of the same foot

Question 19

Gait Parameters - Step Length

Answer 19

distance between point of initial contact of one foot and the point of initial contact of the opposite foot

Question 20

Gait Parameters - Step Width

Answer 20

lateral distance between successive points of opposite feet

Question 21

Gait Parameters - Foot angle

Answer 21

describes an angle between the line of progression and a line drawn between the midpoints of the calcaneous and the second metatarsal head

Question 22

Centre of Mass

Answer 22

is considered the point about which the body is evenly ditributed

Question 23

Free Body Diagrams

Answer 23

A free body diagrams is the link between the complexity of the human situation and the application of the limited, although powerful, techniques of mechanics

Question 24

FBD trying to figure out

Answer 24

1) The joint reaction force
2) The muscle force needed to hold the position

Question 25

FBD Assumptions

Answer 25

1) Static
2) All forces are acting in the same 2D plane
3) Joints are considered hinge joints
4) Muscles under consideration are represented as single muscle equivalent
5) Unknown forces are acting in positive direction