test: centre of mass

Question 1

define: centre of mass

Answer 1

the point at which a body is balanced in all directions

Question 2

if you are standing up and you put your arms above your head, is your COM higher or lower than normal?

Answer 2

higher

Question 3

if you are standing up and you bend your knees, is your COM higher or lower than normal?

Answer 3

lower

Question 4

what is an example of a skill where your COM is outside of your body?

Answer 4

pike jump

Question 5

in the high jump what is the technique called that involves your COM moving outside your body?

Answer 5

fosbury flop

Question 6

why is the fosbury flup so successful?

Answer 6

your COM remains under the bar throughout the jump

Question 7

exam question:

using a sporting example, explain how a performer can move their COM outside the body to effectively perform a named skill (4)

Answer 7

in the fosbury flop, (1)

arching the back moves the COM outside of the body. (1)

the COM will pass underneath the bar while the jumper clears the bar. (1)

therefore the jumper can clear greater heights with the same effort (1)

Question 8

define: stability

Answer 8

the ability of the body to resist motion and remain at rest.

Question 9

what are the 4 things that stability depends on?

Answer 9

• mass of the body: the greater the mass, the greater the inertia and stability
• height of COM: the lower the COM the more stable
• size of base of support: the greater the size of the base (more points of contact), the more stable
• line of gravity: (a line going directly from the COM to the floor) this must be inside the base for the object to be stable)

Question 10

exam question:

explain why a handstand is more difficult than a headstand (3)

Answer 10

headstand has a larger base with 3 points of contact whereas a handstand has 2 points of contact (1)

therefore it is easier to keep the line of gravity over the base in a headstand (1)

so the COM is lower in a headstand than a handstand (1)