KIN 335 - Biomechanics
LAB: Ground Reaction Forces - Linear Kinetics
Reading Assignment: 1) Luhtanen, P. and Komi, P.V. (1978). Segmental contribution to forces in vertical jump.
European Journal of Applied Physiology, 38 (3): 181-188. 2) Harman, E.A., Ro

Trigonometry It is possible to solve many force and velocity problems by drawing vector diagrams. However, the degree of accuracy is dependent upon the exactness of the person doing the drawing and measuring. In addition, this approach is time consuming c

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KIN 335 - Biomechanics
LAB: Projectile Motion
Introduction: Performance in many sport activities is dependent on the ability to either control or predict the motion
of a projectile. In attempting to produce a particular trajectory of a projectile,

EPE 335 - Biomechanics
LAB: Movement Description
Recommended Reading Assignment: Textbook: Chapter 2
Introduction: In order for descriptions of body segments to be meaningful, movement specialists must
be able to communicate with one another using a stand

KIN 335 - Biomechanics
Example Problems: Linear and Angular Kinetics
1) A 75 kg jumper lands stiff-legged on the floor and changes his velocity from 4.5 m/s to zero in 0.15
seconds. Compute the average ground reaction force under his feet during this time

Linear and angular kinematics
How far?
Describing change in linear or angular position Distance (scalar): length of path Displacement (vector): difference between starting and finishing positions; independent of path; as the crow flies Symbols:
linear

Center of Gravity
When gravity acts on a body, every particle
of which it is composed is attracted toward
the earth. The resultant force is the bodys
weight.
Through which point does this resultant
force act?
CENTER OF GRAVITY (CG)
Definitions:
Theore

KIN 335 Biomechanics
Fall 2003
Instructor: Peter F. Vint, Ph.D.
TA : Young Kwan Kim (YK)
General information
Office Hours
M, F 7:30-8:30 am in the classroom
by appointment
Phone Numbers
Cell:
Lab:
480-215-9614
480-965-7528
Web Page:
http:/www.publi

Fluid Mechanics
Fluid Mechanics: the study of forces that
develop when an object moves through a
fluid medium.
Two fluids of interest
Water
Air
Fluid forces
In some cases, fluid forces have little effect
on an objects motion (e.g., shotput)
In other

Impulse-Momentum-Impacts
Momentum: quantity of motion
Any object which has both mass and a velocity is said to have momentum.
M = m.v
(units of measurement: kg.m/s or N.s)
Momentum and Impacts
Momentum is an especially useful measurement in describing

FRICTION
Action Force
Friction
The friction force acts in a direction parallel to the area of contact, and opposes the motion or the tendency to move. The friction force depends on two things:
The normal force (Rn) The nature of the surfaces involved ()

Relationships between linear
and angular motion
Body segment rotations
combine to produce
linear motion of the
whole body or of a
specific point on a body
segment or implement
Joint rotations create
forces on the pedals.
Forces on pedals rotate
crank w

superior
(cranial)
lateral
anterior
(ventral)
medial
NOT SHOWN
posterior
(dorsal)
proximal
inferior
(caudal)
distal
Directional Terms
Distal - farther from trunk
Lateral - away from midline
Anterior - front side in
Proximal - closer to trunk
Medial - clos

KIN 335 Biomechanics
Practice Problems: Uniformly Accelerated Motion
(g = 9.8 m/s2 or 32 ft/s2)
1.
If an athlete jumped 2 feet high and left the ground at an angle of 20 degrees with respect to the
horizontal, how fast was the athlete going in the forward

1.
Two speed skaters (S1 and S2) enter the final curve (point A) with exactly the same velocity (say, 20
m/s). At this instant they are tied. Throughout the first half of the curve (points A-C), it appears that
the athlete in the outside lane (S2) remains

KIN 335 - Biomechanics
Example Problems: Linear and Angular Kinetics
1) A 75 kg jumper lands stiff-legged on the floor and changes his velocity from 4.5 m/s to zero in 0.15
seconds. Compute the average ground reaction force under his feet during this time

Exam 2 Content and Format
Linear kinetics
GRF, net force, Newtons laws
Weight, mass, Law of gravitation
Pressure
Friction
Momentum; impulse; coefficient of
restitution
Centripetal and centrifugal forces
Multiple choice: SCANTRON
Draw and label
Identify a

Stoichiometry Conversion between units can be made very simple if you use the principle of stoichiometry. In general, it is a very good practice to write down the units to each and every quantity entered into a mathematical equation. This is because even

Radial Forces
Remember: objects
must be forced to
follow a curved path
Two forces play a role
in radial acceleration
(action-reaction pair)
aresultant
atangential
aradial
Centripetal force
Centrifugal force
Centripetal force: center seeking force
fo

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Uniformly Accelerated Motion
Under special circumstances, we can
use a series of three equations to
describe or predict movement
Vf = Vi + at
d = Vit + 1/2at2
Vf2 = Vi2 + 2ad
Most often, these equations are used to
describe either horizontal or vertical

Conversions and Constants:
1 in = 2.54 cm
1 mi = 1.61 km
1 lb = 4.45 N
1 rev = 2 rad = 360
G = 6.673 1011 Nm2/kg2
g = 9.8 m/s2 = 32 ft/s2
KIN 335 - Biomechanics
Helpful Equations
v f = v i + at
c
a
1 2
at
2
v 2 = v i2 + 2ad
f
d = vi t +
d H = v H t TOTAL

KIN 335 - Biomechanics
Impacts and the Coefficient of Restitution
Reading Assignment: Bernardo, S. (May, 1984). Physics of the sweet spot. Science Digest, pp.
62-65, 95; Bryant, F.O., Burkett, L.N., Chen, S.S., Krahenbuhl, G.S., & Lu, P. (1977).
Dynamic a

BONUS #1 The Klap Skate
Describe the problem that brought
about this innovation in speed
skating equipment.
Describe the innovation
What does it do?
Which specific mechanical
principle does this skate address
and how does it really work? Be
specific.
H

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KIN 335 - Biomechanics
PROBLEM SET 1
Instructions: Read each question carefully. On a separate sheet of paper, complete each
problem and label your final answer clearly. Make sure that you show all of your work for full
credit.
1. A new trail leads

Curvy Stuff Practice Problems
The curves provided on the following pages represent instantaneous profiles of
displacement (D), velocity (V), or acceleration (A) with respect to time (T). For each
curve, enter the most appropriate time (Ti) that represents