The Turning Effect of Forces
You should be able to:
•state what the centre of gravity of an object is.
•describe a simple experiment to determine the
centre of gravity of an object.
•define and apply the moment of force.
•apply the principle of moments to solve
problems, including the human forearm.
The Turning Effect of Forces
Describe an experiment to find the centre of gravity of an object.
1. Suspend object from a point
2. Use plumb line to find the vertical
line and mark it on with a pencil
3. Hang from another point and
draw another vertical line
4. Where the lines intersect gives
position of centre of gravity
5. Check your centre of gravity by
choosing another point and
repeating.
The Turning Effect of Forces
Centre of Gravity – the point
where the weight of an object
can be considered to act.
The Turning Effect of Forces
Centre of Gravity
The Turning Effect of Forces
Define and apply the moment of force
The Turning Effect of Forces
Define and apply the moment of force
The Turning Effect of Forces
Define and apply the moment of force
The Turning Effect of Forces
Define and apply the moment of force
The Turning Effect of Forces
Define and apply the moment of force
Use the equipment available to find ;
1) The mass of the rule
2) The mass of the unknown weight
The Turning Effect of Forces
Define and apply the moment of force
The Turning Effect of Forces
Define and apply the moment of force
The Turning Effect of Forces
Define and apply the moment of force
The Turning Effect of Forces
You should be able to:
•define and apply the torque of a couple
•explain that both the net force and net moment
on an object in equilibrium is zero
•apply the principle of moments to solve
problems where the perpendicular force has to
be calculated.
The Turning Effect of Forces
Couple
The Turning Effect of Forces
What is the significance of this diagram ?
The Turning Effect of Forces
What is the counterweight (W) required to
balance the light crane arm shown in
diagram ?
5m
60o
3m
70 kg
W
The Turning Effect of Forces
What is the tension (T) in the cable shown
in diagram ?
T
1.5 m
70o
3m
20 N
The Turning Effect of Forces
What is the tension (T) in the cable shown
in diagram?
T
25 m
20 m
70 N
65o
Typical loading diagram