Turning Forces, Centre Of Gravity

Question 1

A lever

Answer 1

Is any rigid body which is free to turn about a fixed point called the fulcrum.

Question 2

Examples of levers:

Answer 2

Door, door handle, pliers, scissors, metre stick, screwdriver (used to open paint tin), etc.

Question 3

The Law of the Lever

Answer 3

States that when a lever (e.g. a metre stick) is balanced, the total clockwise moments equal the total anticlockwise moments.

Question 4

The centre of gravity

Answer 4

Of an object is the point through which all the weight of the object appears to act. (i.e. the centre of its weight).

Question 5

Stable equilibrium

Answer 5

Is present if when an object is slightly tilted, its centre of gravity is raised, and it goes back to original position on release.

Question 6

Unstable equilibrium

Answer 6

Is present if when an object is slightly tilted, it’s centre of gravity is lowered, and it takes a new position when released (i.e. it falls over on its side).

Question 7

Neutral equilibrium

Answer 7

Is present if when an object is moved, its centre of gravity is neither raised nor lowered. The object never becomes unstable - it does not fall over and just takes up a new position where it is still in neutral equilibrium.

Question 8

The moment

Answer 8

Of a force is the turning effect of a force.

Moment = (Force) x (Distance from the fulcrum).