Turning effect of Forces and Stability Flashcards
Formula and unit for moment
Moment = force x distance
Unit: Nm
Define moment
The product of force and the perpendicular distance from the pivot
State the principle of moment
The principle of moment states that an object will balance horizontally on a pivot only if the sum of all clockwise moment is equal to the sum of all anticlockwise moment
Describe an experiment to verify the principle of moment (4 steps)
1) A rod is balanced horizontally on a pivot
2) A known mass is placed at a distance on one side of the pivot. Calculate its moment.
3) Another known mass is placed on the other side of the pivot and is adjusted until the rod is in equilibrium. Calculate its moment
4) If both moments are equal the experiment is a success
* labelled diagram*
Define centre of gravity/mass
The point at which the mass of an object acts for any orientation of the object
Describe an experiment to find the centre of gravity of a lamina/irregular object (5 steps)
1) 3 holes (A, B, C) are made at different corners of the lamina
2) The lamina is hung at hole A using a pin
3) A plumbline (string+bob) is attached to the pin and a line is drawn on the lamina behind the plumbline
4) The lamina is hung at holes B and C. Step 3 is repeated each time
5) The point of intersection of the lines give the position of centre of gravity
* labelled diagram*
When will an object be more stable?
1) Its position of gravity is lower
2) It has a large surface area of contact
Why are racing cars flat and have wide tyres?
Wide tyres increase the area of contact and they are flat so there is a lower centre of gravity
What does the counterweight on a crane do?
Keeps the arm of the crane in equilibrium
Why can the counterweight move along the arm of a crane?
So that objects of different masses can be lifted without adding/removing counterweight
