# ESS 303 -- Biomechanics

Mechanics

Nov 13, 2013 (4 years and 7 months ago)

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ESS 303

Biomechanics

Angular Kinematics

From Last Time

Someone kicks a football so that it travels at a
velocity of 29.7m/s at an angle of 22
°

above
the ground

What was the vertical component of velocity?

What was the horizontal component of velocity?

SOH (sin of an angle = opposite / hypotenuse)

sin 22 = Y / 29.7m/s

Y = sin 22 * 29.7m/s =
11.13m/s

CAH (cos of an angle = adjacent / hypotenuse)

cos 22 = X / 29.7m/s

X = cos 22 * 29.7m/s =
27.54m/s

Angular Kinematics

The branch of biomechanics that deals
with the description of the angular
components of motion

Uses degrees or radians to describe
position and/or movement

Degree: 360
°

in a circle

of a circle

Angular Kinematics

In the drawing to
the right

A, B &
C have the same
angular
displacement or
rotation

A, B & C have
different linear
displacements

A B C

A B C

Angular Kinematics

θ = S/R

S = displacement
along the arc

C = 3m and each had
a rotation of 90
°
,
what were the
displacements of
each?

A B C

A B C

Angular Kinematics

90
°

SA =
1.57m

SB =
3.14m

SC =
4.71m

A B C

A B C

Angle Types

Relative:

angle between segments

Absolute:

describes the orientation of
an object in space

(7,9)

(5,5)

Y
proximal

-

Y
distal

Tan θ =
–––––––––––––

X
proximal

-

X
distal

Femoral Angle =
63.43
°

Right Hand Rule

Today’s Formulas

θ = S/R (remember to use radians here)

Tan θ = (Y
proximal

Y
distal
)/(X
proximal

X
distal
)

Angular speed = angular distance/time

Angular velocity (
ω
) =
∆θ / ∆t

Angular acceleration (α) = ∆ω / ∆t

Problems

A figure skater turns 6 ½ times

What was the angular distance traveled?

What was the angular displacement?

While watching a golf swing, you note
that the angular velocity at time
1

(0.05s)