The Presentation consists of Reaction Board Method Practical that is a part of Sports Biomechanics Syllabus at Graduation and Post-graduation level at University of Delhi.

1. PRACTICAL NO.2:
DETERMINATION OF CENTER
OF GRAVITY BY REACTION
BOARD METHOD
PREPARED BY:
Ms. Rabiya Husain
Lecturer, IGIPESS
University of Delhi

2. PREREQUISITE KNOWLEDGE
 Force
 Law of Action-Reaction
 Torque
 Center of Gravity
 Equilibrium

3. PREREQUISITE KNOWLEDGE
Force
 “It is the push or pull
exerted by a body/system
on other body/system”
 S.I Unit- Newton (N).
Law of Action and Reaction
 “Action force=Reaction
force”

4. PREREQUISITE KNOWLEDGE
Torque
 “measure of the force that can cause an
object to rotate about an axis.”
 Τ = Force.Moment Arm.
 S.I unit = Newton.meter (Nm).

5. PREREQUISITE KNOWLEDGE
Center of Gravity (C.O.G.)
 “Point at which all parts of body exactly balance
each other and where entire weight of body is
concentrated.”
Equilibrium
 The state where net forces= 0.

6. REACTION BOARD
 Method to determine Center of Gravity of a
living being in supine position.

7. AIM & REQUIREMENTS
 To determine the height of center of gravity
using reaction board method.
Requirements
 A board of length 1.83 m.
 One subject.
 Weighing machine.

8. PROCEDURE
 Board will be placed horizontally on the knife
edges : one on block of wood & another on
platform of weighing machine.
 Initial reading will be recorded(R1).

9. PROCEDURE
 Then subject lies in supine position on board.
 New reading(R2) will be recorded.
 As, board was in equilibrium before subject laid
on it , and it is again in equilibrium thus, forces &
moment introduced are in equilibrium.

10. PROCEDURE
Introduced forces are: 1.Weight of subject
2. Reaction to weight
force.
 Consider moments rotate about
 Moment of Reaction weight force= (R2-
R1).L

11. PROCEDURE
 Moment of weight force= W.x
 As they are equilibrium = W.x = (R2-R1).L
 x = (R2-R1).L
W

12. CALCULATE
If W= 52
R2=31.2, R1= 10.7
what is the location of C.O.G
using Reaction board method
(board length=1.8 meters).

13. CALCULATION
 x = (R2-R1).L
W
Where, R2 = 31.2
R1 = 10.7
W = 52
x = (31.2 – 10.7) x 1.8
52
= 0.39 x 1.8 = 0.70 m
The height of the centre of gravity of the subject by reaction
board method is determined as x = 0.7m.

14. FULL PRACTICAL
 For full practical consult:
Shaw, D. (2007).
Mechanical Basis of
Biomechanics. New
Delhi: Khel Sahitya
Kendra.