mechanics-scalars,vectors,moments Flashcards
What is a scalar quantity ?
A quantity with only magnitude.
what is a vector quantity ?
A quantity with magnitude and direction.
Give 3 examples of scalar quantities.
speed
temperature
distance
pressure
energy
power
etc.
Give 3 examples of vector quantities.
weight
displacement
momentum
acceleration
force
etc.
What is the resultant force of a box 5N right and 3N left ?
2N right
How would you find the resultant force of a object with perpendicular forces (right angles) ?
Using Pythagoras or scale drawing.
How do you find components of a force ?
Use Pythagoras or trigonometry depending on the variables given.
What does it mean when a system is in equilibrium ?
The resultant force is 0 and the resultant moment is 0 so the system is either stationary or at a constant velocity.
what are coplanar forces ?
forces that act along the same plane.
For a object in equillibrium on a inclined plane what is the friction equal to ?
The parallel component of the weight
For a object on a inclined plane what is the normal contact equal to ?
The perpendicular component of the weight.
For a object on a inclined plane what is the angle between the weight and the perpendicular component of the weight equal to ?
The angle of the slope.
For a object on a inclined plane what part of a triangle is the weight ?
Hypotenuse.
How do you work out the parallel component of the weight for a object on a slope ?
Wsinθ.
How do you find the perpendicular component of the weight for a object on a slope ?
wcosθ.
List 3 types of a force e.g. weight
weight
air resistance
thrust
What is the difference between mass and weight ?
Weight is the force exerted by gravity the mass is a measure of the amount of material.
What is the centre of mass ?
Point at which gravity acts upon.
When will a object start to topple ?
When its centre of mass falls outside its base.
What is a moment ?
Force multiplied by perpendicular distance.
What is the unit for a moment ?
Newton metre (NM).
If the distance=1m and Force=5 what is the moment ?
5NM.
How do you find the moment of a force that isn’t perpendicular ?
Find perpendicular force or distance.
What is the principle of moments ?
For a system in equilibrium the clockwise moments=anti-clockwise moments about any point
If a object is uniform where is its centre of mass ?
Its physical centre.
For a double pivot what is the moments about 1 pivot equal to ?
The normal contact of the other pivot.
What is a couple ?
Two opposite and equal coplanar forces that are along the same line of action.
