5. Rotational Motion

Question 1

What is the Center of Gravity?
(aka Center of mass)

Answer 1

• The point around which a system’s weight is equally distributed in all directions
• Point around which the masses are balanced

Question 2

What does the Center of Gravity determine?

Answer 2

The position of the center of gravity determines how the body responds to external forces (i.e., control)

Question 3

Where is the Center of Mass of an object located?

Answer 3

• Not a fixed position
• May be outside of the physical body

Question 4

How does an object behave if a force acts directly at the centre of gravity?

Answer 4

It will produce translation only

Question 5

What is Centric Force?

Answer 5

• Centric Force acts at the centre of gravity of a system
• Resulting in linear motion only.

Question 6

How does an object behave if a force acts away from the centre of gravity?

Answer 6

It will produce some Translation and Rotation

Question 7

What is an Eccentric Force?

Answer 7

• Ecentric forces act off the centre of gravity of a system
• Results in rotation and curvilinear motion
• Any eccentric force will cause rotation

Question 8

How does an object behave when two forces that are equal in magnitude but opposite in direction, act awat from the centre of gravity?

Answer 8

• The Results is Pure Moment
• aka Pure Rotation

Question 9

What is a “Couple”?

Answer 9

A couple is 2 eccentric forces that cause pure roation (no translation)

Question 10

How does a linear force create rotation?

Answer 10

• Any force applied away from the anchor point will rotate the object about the axis
• Anchor Point = Axis of Rotation = Fulcrum = Pivot Point