Centre of mass and moments Flashcards
(9 cards)
What is the centre of mass?
the point on a object at which the mass of the object may be thought to be concentrated
Where is the centre of mass on a symetrical object?
along the axes of symettry
How do you find the centre of mass by suspending the object?
drill a hole in the object and hang it so it is free to swing
hang a plumb line from the suspension point
marks the vertical line directly below the suspension point
hang it again in a different location and mark the vertical line
where the lines cross is the centre of mass
What is a pendulum?
a plumb line is an example of a pendulum
the pendulum is free to swing
at the highest point of the swing there is no kinetic energy but maximum gravitational potentiol energy
while swinging, there is a high KE and low GP
e.g. playground swing, fairground rides
What is a moment and what does the size of a moment depend on?
the turning effect off a force
size of force applied
perpendicular distance from pivot to the line of action of the force
What are the moments on a object not turning?
If an object is not turning, the total clockwise moment must be exactly balanced by the total anticlockwise moment about any pivot
How do levers reduce the force needed to perform tasks?
levers rely on the principle of moments to act as force multiplies
the reduce the effort needed to move a load by increasing the distance over which the force is acting
How can you calculate how to balance moments?
1) work out the moment for which you have been given all the infomation
2) change the subject of the equation to calculate the force
How does a object fall?
if the line of action of the stools weight falls outside the base of the stool the stool will topple
due to the anti-clockwise moment being greater than the clockwise moment
