MECHANICS Flashcards
Scalar
a quantity with no direction and has magnitude
Vector
a quantity with magnitude and direction
name examples of scalars
- length/distance
- speed
- mass
- temperature
- time
- energy
name examples of vectors
- displacement
- velocity
- force
- acceleration
- momentum
Moment
the turning effect of a force around a turning point
What does a moment of a force depend on
- size of the force
- how far the force is applied from the turning point
equation for moments
moment (Nm) = force (N) * distance (m)
what is the principle of moments
for a body to be in equilibrium, the sum of clockwise moments about any point equals the sum of the anticlockwise moments about the same point.
couples
a pair of forces of equal size which act parallel to each other, but in opposite directions.
centre of mass
the single point that you consider its whole length can act through (whatever its orientation).
- the object will balance around this point
How to find the centre of mass by experiment
- Hang the object freely from a point
- Draw a vertical line downwards from the point of suspension - use a plumb bob to get your line exactly vertical
- Hang the object from a different point and draw another vertical line
- The centre of mass is where the two lines cross
Speed
how fast something is moving regardless of direction
displacement
how far an objects travelled from its starting point in a given direction
velocity
the rate of change of an objects displacement (its speed in a given direction)
acceleration
the rate of change of an objects velocity
