Chapter 3 - Applications of forces Flashcards
In hooke’s law how do you find the extension ?
extension = extended length - natural length
What is the definition of hooke’s law ?
Extension is proportional to the load, provided the proportional limit is not exceeded.
What is the equation for hooke’s law ?
F = k x e
k = spring constant e = extension F = force
What does the term pressure mean ?
how force is distributed normally (at right angles) over an area.
What is the equation of pressure ?
force
Pressure = —————-
area
What are the units of pressure ?
N/m^2 (commonly called pascals (Pa))
What factors does the size of the moment depend on ?
- the size of the force
- the distance the force is from the pivot
What’s the equation for moments ?
moment = force x perpendicular distance from the pivot
What is the unit of a moment ?
Newton meter (Nm)
What is the principle of moments ?
When a body is in equilibrium, the sum of the clockwise moments about any point equals the sum of the anticlockwise moments about the same point.
What is the formula for the principle of moments ?
F1 x d1 = F2 x d2
What is an objects centre of gravity (mass) ?
A point at which we can consider all their weight to be concentrated.
What is a lamina ?
A body in the form of a flat thin sheet.
How do you fin the centre of gravity in an irregular lamina ?
1 - hang the shape from a pin embedded into a cork
2- Hang a plumb line from the same pin
3- when the lamina settles mark the vertical line
4- repeat for two further points
5- The intersection of these lines is the COG
When is a body in equilibrium ?
When the resultant force and resultant turning effect on it are zero.
