Center of Gravity - Biomechanics of the Human Body - page 48

Example 3.3 Find the coordinates of the C.G. of the figure of Example 3.3:

y (m)

6

50 kg

4

50 kg

2

50 kg

0

x (m)

0 2 4 6

ð Þ ðÞþ ð Þ ðÞþ ð Þ ðÞ

50kg 2m 50kg 1m 50kg 4m

x C : G : ¼ ¼ 2 33m

:

150kg

ð 50kg Þ ðÞþ 1m ð 50kg Þ ðÞþ 4m ð 50kg Þ ðÞ 5m

y C : G : ¼ ¼ 3 33m

: :

150kg

In this case, the center of gravity does not belong to the body.

Exercise 3.5 Find the coordinates of the C.G. of the figure of Exercise 3.5:

y (cm)

4

3

25 g

2

1

25 g

0 -2

-1 0 1 2 x (cm)

Example 3.4 Consider a seated person whose lower leg is vertical, as shown in
the figure of Example 3.4. The coordinates of the center of mass of the thigh, leg,
and foot are listed in the table of Example 3.4. The masses of thigh, leg, and
foot are, respectively, 0.106 M , 0.046 M , and 0.017 M , with M the total mass of
the body. Find the center of gravity of the set thigh/leg/foot of this person in
this posture.