Lab#2 Bouncing BallSupplemental Testing

Experiments and analysis performed by Mike Krieg

Ultra High Speed Video

•High speed video taken using Phantom v4.3 high speed camera

•Video filmed at 1200 fps

•Racquetball dropped from ~3.5ft

Analysis

0 0.005 0.01 0.015 0.02 0.025 0.03 0.035-1

0

1

2

3

4

5

Time (s)

Po

siti

on

(in

)

Top

BottomGeometric Center

•Video was analyzed frame by frame to extract racquetball positions throughout impact.

•Positions determined for top and bottom of ball (middle taken as average)

•2 independent methods were employed to determine restitution coefficient from position data

Velocity Method

0 0.005 0.01 0.015 0.02 0.025 0.03 0.035-200

-150

-100

-50

0

50

100

150

200

250

Time (s)

Ve

loc

ity

(in

/s)

sinVimpact 181

sinVreflex 162

impact

reflexvelocity V

Ve

According to the velocity method the coefficient of restitution was determined to be 0.8950

Ball Deflection Method

0 0.005 0.01 0.015 0.02 0.025 0.03 0.035-0.05

0

0.05

0.1

0.15

0.2

0.25

0.3

Time (s)

Ba

ll C

om

pre

ss

ion

(in

)

Coefficient defined by ratio of reaction impulses during impact

tc

t

t

tc

dtR

dtRe

1

2

Reaction forces approximated using Hooke’s Law

tc

t

t

tctc

t

t

tc

dt

dt

dtk

dtke

1

2

1

2

According to the deflection method the coefficient of restitution was determined to be 0.8693