Mechanics Flashcards
What is a vector?
A physical quantity that has a direction as well as a magnitude.
Examples of vectors.
Field strength, force, momentum, velocity, acceleration, displacement.
What is a scaler?
A physical quantity that is not directional.
Examples of scalars?
Density, charge, resistance, energy, distance, speed.
How can a vector be represented?
An arrow
What does the length of an arrow representing a vector determine?
The magnitude of the vector quantity.
If two forces act on an object, when is equilibrium achieved?
When the two forces are equal and opposite.
What are the ways to work out forces on an object when it is in equilibrium?
Vector triangle or resolving the components.
What is the centre of mass of an object?
The point through which the entire mass of the object may be considered to act.
Moment equation?
Moment = force x perpendicular distance from the line of action of the force to the pivot
What is the principle of moments?
For any object that is in equilibrium, the sum of the clockwise moments about a point is equal to the sum of the anticlockwise moments about that same point.
What is a couple?
A pair of equal and opposite coplanar force, not acting the same straight line.
Moment of a couple equation?
Moment = force x the perpendicular distance between the lines of action of the forces
What are the two conditions of equilibrium?
There is no resultant force.
There is no turning effect about any point.
How do you find the centre of mass of symmetrical objects?
Along the line of symmetry, or where multiple lines of symmetry intersect.
How do you find the centre of mass of a non-symmetrical object?
When an object that has been left to swing freely stops swinging, the centre of mass is on a vertical line passing through the pivot.
When an object is in equilibrium, what is true of the vertical forces?
They are equal in magnitude and opposite in direction.
When an object is in equilibrium, what is true of the horizontal forces?
They are equal in magnitude and opposite in direction.
When an object in equilibrum is supported at one point, what is the support force equal to?
It is equal and opposite to the total downward force acting on the object
What do the symbols stand for?
v = s/t
v = velocity, s = distance, t = time
What do the symbols stand for?
a = Δv/t
a = acceleration, Δv = change in velocity, t = time
How do you calculate average velocity?
Displacement / time
Define velocity.
The rate of change of displacement.
Define acceleration.
The rate of change of velocity.
