Mechanics 1 - Scalars, Vectors and Moments

Question 1

What is meant by centre of mass?

Answer 1

The point in a body where the weight of the object appears to act

Also the resultant moment about this point = 0

Question 2

Define the moment of a force

Answer 2

Product of the force and the perpendicular distance from the line of action of the force to the point

Question 3

State the principle of moments

Answer 3

Sum of the clockwise moments about a point is equal to the sum of the anticlockwise moments for a system in equilibrium

Question 4

How is the balancing force different from the resultant force?

Answer 4

The balancing force brings the object into equilibrium so makes the resultant force = 0

For a scale drawing, it is the vector that closes the shape

Question 5

What is a couple?

Answer 5

A pair of equal and opposite coplanar forces which do not act along the same line of action

Question 6

What does it mean if an object is uniform?

Answer 6

It has an constant density so its centre of mass acts from the physical centre point of the object

(Weight vector starts from middle of object)