Biomechanics Linear Kinematics

What is kinematics?

spatial and temporal components of motion

What is a reference system used for?

to express the position of an object

What is an absolute reference system?

where position and angle are expressed with respect to a fixed point or line

What is a relative reference system?

where movement of a segment is described relative to an adjacent segment that is moveable

What is an example of an absolute reference system?

the knee relative to the ground

What is an example of a relative reference system?

the knee relative to the thigh

What does displacement concern?

magnitude and direction

How is displacement different from distance?

displacement is a straight line from start to end

What is speed?

rate of change relative to a position

What is linear velocity?

the change in displacement over the change in time

How many steps are in a stride?

2

What is the stride rate?

the number of strides per second

How can gait speed be increased?

by increasing either stride length or stride rate

What variable primarily increases when going from jogging to medium speeds?

stride length

What variable primarily increases when going from medium speeds to sprinting?

stride rate

What is the gradient or slope?

change in position over change in time

What is the temporal midpoint?

the average of a single velocity point

What is the first central difference method?

a method to find the temporal midpoint; involves using the point before and after our desired point to determine the velocity

What is the benefit of the first central difference method?

gives a better estimate of instantaneous velocity when time difference is small

What is linear acceleration?

the rate of change in linear velocity

What is acceleration when velocity is constant?

0

When a velocity curve is increasing, acceleration is increasing or decreasing?

increasing

When direction is moving to the right, acceleration is positive or negative?

positive

When velocity is increasing to the left, acceleration is positive or negative?

negative

When velocity is decreasing to the right, acceleration is positive or negative?

negative

What is the Riemann Sum?

approximating the area under a curve using rectangles

What are the two parts that make up a stride?

stance phase and swing phase

When is stance phase?

when the foot is in contact with the ground

What is swing phase?

when the foot has gone through “toe off” and is moving to the next step

What type of movement has no double stance?

running

About how much stance phase occurs during jogging?

50%

About how much stance phase occurs during fast running?

30%

About how much stance phase occurs during sprinting?

20%

Using digitization, calculating shoulder abduction and adduction during a jumping jack is a qualitative analysis T/F

False

During a long jump, only translational motion occurs T/F

false

Is velocity a vector?

yes

What is acceleration defined by?

the time rate of change of velocity

Are displacement and distance both scalar quantities?

no, displacement is a vector

What is the slope of a line tangent to a velocity by time curve?

acceleration

What is the area under a velocity by time graph?

displacement

What direction is motion if the acceleration is negative?

to the left

What does the maximum point on a position by time graph indicate for velocity?

that velocity is constant or = 0

Is change in velocity equal to the area under an acceleration by time curve?

yes

Are stride length and step length synonymous?

no

During sprinting, a greater percentage of the gait cycle is spent in stance relative to walking T/F

false

At faster walking speeds, one first increases step rate and then stride length T/F

false