Flashcards in Mechanics Deck (169)
What is a scalar quantity?
A quantity that has no direction (just an amount)
What is a vector quantity?
A quantity that has magnitude and direction
Give 4 examples of scalar quantities
Give 4 examples of vector quantities
What is a bearing?
A 3-digit angle that is measured clockwise from north in degrees
How do you find the resultant vector?
By adding 2 or more vectors together
How do you find the resultant vector from a scale diagram?
Drawing a scale diagram with all the vectors joining in one line (tip-to-tail), then measuring the length and angle of the resultant vector from the diagram
What is displacement?
The position relative to the start position
What does cos60 and sin30 equal?
What is an inclined plane?
Which direction does weight always act?
What is happening when is a body is in equilibrium?
All the forces are balanced (no resultant force)
What 2 states can an object in equilibrium be at?
Rest or moving with constant velocity
When only 2 forces act on an object, what do they have to be for the object to be in equilibrium?
Equal and opposite (opposite direction)
When forces act on an object in equilibrium, what do they form if you draw them tip-to-tail in a scale diagram?
Form a closed loop (a vector triangle)
What is the magnitude of a vector?
The size of it (without direction)
What is a moment of a force?
The turning point of a force around a point
What are 2 moments of equal size acting parallel to each other called?
What is the mass of an object defined as?
The amount of matter in it
What is inertia?
A resistance to a change in motion
What happens to the inertia if an objects mass is increased?
The greater the resistance to a change in motion will be (larger inertia)
What is weight and what is it measured in?
A force measured in newtons
The force experienced by a mass due to gravity
What equation links weight, gravity field strength and mass
Is weight a scalar or vector quantity?
Vector as it has size and direction
What 2 things does the moment of a force depend on?
Size of the force and how far the force is applied from the turning point
What equation links moment, force and perpendicular distance from the turning point?
M = fd
What does the principle of moment state for a body to be at equilibrium?
The sum of the clockwise moments about any point equals the sum of the anti-clockwise moments at the same point
What will happen to an object if the moments aren't balanced?
The object will turn