Forces in Equilibrium

Question 1

What is the difference between a vector and a scalar?

Answer 1

A vector is any physical quantity that has a direction and a magnitude. Where as a scalar is any physical quantity that is not directional.

Question 2

What is the principle of moments?

Answer 2

An object is in equilibrium when..

the sum of the clockwise moments = the sum of the anticlockwise moments

Question 3

For a triangle where P is the hypotenuse, and Y is the angle between P and the adjacent (A), how would you calculate the size of the adjacent (A)?

Answer 3

P cos(y)

Question 4

For a stationary object the resultant force is…

Answer 4

Zero

Question 5

If two forces are acting perpendicular to each other, how can you find the magnitude of the resultant force?

Answer 5

Pythagoras’ theorem [A^2+B^2=C^2]

Question 6

How do you calculate the moment of a force?

Answer 6

Force x Perpendicular distance from the point of action.

Question 7

What is a moment?

Answer 7

The turning effect of a force

Question 8

What are the units for a moment?

Answer 8

Nm

Question 9

What is the difference between stable and unstable equilibrium?

Answer 9

An object is in stable equilibrium if it can be displaced, and it will return to its original position.

[eg. a ball on a string]

An object is in unstable equilibrium if it can be displaced, but will not return to its original position.

[eg. a plank resting on a round ball]

Question 10

What is the resultant force for an object moving at a constant velocity?

Answer 10

Zero

Question 11

How can you get an object to ‘topple’ ?

Answer 11

Move the line of action of weight (a line vertically down from the centre of mass) outside of its base area.