Unit 3 - Centre of Mass, Moments and Stability Flashcards
What is a moment?
A turning effect of a force
What is the equation for moments?
moment = force x perpendicular distance from axis of rotation
Where does the centre of mass hang?
Directly below the point of suspension
How can you find the centre of mass of any flat shape?
- Suspend the shape and a plumb line from the same point, and wait until they stop moving
- Draw a line along the plumb line
- Do the same thing again, but suspend the shape from a different pivot
- The centre of mass is where your lines cross
In simple shapes how can you guess where the centre of mass will be?
By looking at the lines of symmetry
What happens if the anticlockwise moments are equal to the clockwise moments?
The object wont turn
What do levers do?
Reduce the amount of force that’s needed to get the same moment by increasing the distance
→ They make it easier to do work by moving the distance the force is applied further from the pivot
3 examples of levers?
Long sticks or bars, wheelbarrows and scissors
If the total anticlockwise moments do not equal the total clockwise moments, what will happen?
A resultant moment, therefore the object will turn
When will an object begin to tip over?
If its centre of mass moves beyond the edge of its base (if the line of action no longer acts over the base)
What does the time it takes for a pendulum to swing depend on?
It’s length
Pendulums: what is the time period
The time taken for the pendulum to swing from one side to the other and back again
Pendulums: how can the time period be calculated? (equation)
Time period = 1 / frequency
What are some examples of circular motion?
The earth orbiting the sun
A car corniering
Electron orbiting the nucleus
What is velocity?
Speed in a given direction
