# Coefficient of Restitution (Cor) of 3 Balls

Topics: Balls, Table tennis, Ball Pages: 6 (979 words) Published: March 20, 2007
How does the COR affect different types of sports balls bounce on different types of surfaces?

AIM  the aim of this experiment is to find out how the COR (coefficient of restitution) of 3 balls (tennis ball, snooker ball and ping pong ball).

FORMULA USED FOR COR 

GPE (after)= KE (after)
GPE (before)=KE (before)

mxgxHr=½ x mx Vout²
mxgxHd ½ x m Vin²

Hr=Vout²
Hd Vin²

APPARATUS
meter stick,
tennis ball,
ping pong ball,
snooker ball,
surfaces; wood and carpet

METHOD - I will firstly organize all the apparatus that are needed for this experiment. 1.I will make 3 tables for my results to be recorded in.
2.Then I will get my partner to hold the meter stick firmly with one hand. 3.In the other hand of my partner, the first ball will be held. 4.My partner will drop the ball from a height of 100cm.

5.I will keep at eye level and watch closely
6.I will record the height, to the nearest cm, of the highest point that the ball bounces to. 7.I will repeat this method ten times on wood, and then ten times on carpet. 8.I will then bring into play the two other balls, and do the same as I have done with the first ball.

PREDICTION  I predict that the tennis ball will bounce higher on wood than the other two balls. Reason being that the tennis ball is lighter than the snooker ball and requires less force. The material used is also a factor that will help it bounce higher than the ping pong ball.

RISK ASSESMENT 

Item Risk Reduce hazardImplementation
All balls used
(football, tennis ball, ping pong ball)Some balls may be heavy and hurt someoneBe sure to keep a safe distance When I let go of the ball, I made sure I moved back.

There were no other significant hazards.

DIAGRAM OF EXPERMIMENT-

Results -

Tennis Ball -

On carpet (cm)On wood (cm)
1st bounce 4547
2nd bounce4455
3rd bounce4356
4th bounce4545
5th bounce4352
6th bounce5153
7th bounce4352
8th bounce4256
9th bounce4354
10th bounce4453
Average 44.352.3
COR0.670.72

Average on Wood =

47+55+56+45+52+53+52+56+54+53 = 523cm/10 = 52.3 cm

Anomalous = 51

COR = 52.3 / 100 = 0.72

Average on Carpet =

45+44+43+45+43+51+43+42+43+44 = 443cm/10 = 44.3cm

Anomalous = 47, 45

COR = 44.3 / 100 = 0.67

I can say, by observing my table of results, the ball bounces higher on the wooden surface in comparison to the carpeted surface.

Ping pong ball -

On carpet (cm)On wood (cm)
1st bounce 4354
2nd bounce4258
3rd bounce5859
4th bounce4352
5th bounce4555
6th bounce4254
7th bounce4655
8th bounce4344
9th bounce4352
10th bounce4454
Average44.9cm53.7cm
COR0.670.73

Average on Carpet =
43+42+58+43+45+42+46+43+43+44 = 449cm / 10 = 44.9cm

Anomalous = 58

COR = 44.9/ 100 = 0.67

Average on Wood =
54+52+55+54+55+52+54+58+59+44 = 537cm / 10 = 53.7cm

Anomalous = 58, 59, 44

COR = 53.7 / 100 = 0.73

I have noticed that my results show that the ping pong ball bounces higher on the wooden surface.

Snooker ball -
On carpet (cm)On wood (cm)
1st bounce 157
2nd bounce147
3rd bounce146
4th bounce135
5th bounce147
6th bounce168
7th bounce134
8th bounce137
9th bounce147
10th bounce128
Average 13.86.6
COR0.370.26

Average on Carpet =
7+7+6+5+7+8+4+7+7+8 = 66cm / 10 = 6.6cm

Anomalous = None

COR = 13.8/ 100 = 0.37

Average on Wood =
15+14+14+13+14+16+13+13+14+12 = 138cm / 10 = 13.8cm

Anomalous = 5, 4

COR = 6.6 / 100 = 0.26

By looking at my results I can see that the snooker ball bounces higher on carpet than it does on the wooden surface.
COR - Next I worked out the COR of the 3 balls. The COR measures how much bounce there is in a ball.

The table below shows the results for the COR for all the averages of the bounce height.

MaterialTennis ball Snooker ballPing pong ball
Wood 0.720.260.73...