Modelling Flashcards
What are SI units?
They stand for Standard International Units, and are the set of internationally used units.
What is m/s or m/s2 derived from?
ms-1 or ms-2
What are models used for?
To apply mathematics to simulate real-life problems and solve them.
We must make many assumptions to do this.
What does an object being ‘light’ represent?
The body has negligible mass.
What does an object being ‘static’ represent?
The body is not in motion.
What does an object being ‘rough’ represent?
A body in contact with the surface will experience a frictional force, opposing motion.
What does an object being ‘smooth’ represent?
A body in contact with the surface will experience a frictional force.
What does an object being ‘rigid’ represent?
The body doesn’t bend.
What does an object being ‘thin’ represent?
The body has negligible thickness.
What does an object being ‘inextensible’ represent?
The body can’t be stretched.
What does an object being in ‘equilibrium’ represent?
There is no resultant force acting on the body.
What does an object being a ‘rod’ represent?
All dimensions of the object except for one are negligible.
What does an object being a ‘lamina’ represent?
The object has an area but negligible thickness.
What does an object being ‘uniform’ represent?
Mass is distributed evenly.
What does an object being a ‘wire’ represent?
The object is a rigid thin length of metal.
What does an object being a ‘bead’ represent?
It is a particle with a hole for threading a wire or string.
What does an object being a ‘peg’ represent?
It is a support from which a body can be suspended or rested.
What does ‘air resistance’ represent?
Resistance experienced as an object moves through the air.
What does ‘gravity’ represent?
The force of attraction of all objects with mass upon each other.
What does a ‘pulley’ represent?
A wheel, usually modelled as fixed and smooth over which a string passes.
What does a ‘plane’ represent?
A flat surface.
What are other names for a reaction force?
The ‘normal’ force or ‘boyance’
Of the following quantities, specify which are vectors and which are scalars:
Displacement
Velocity
Distance
Time
Speed
Mass
Acceleration
Force/weight
Scalars: Distance, time, speed, mass
Vectors: Displacement, velocity, accleration, force/weight.
What does negative acceleration represent?
Deceleration
How do you write a column vector of 3 across, 4 up?
(3)
(4)
If vectors have the same direction, but are factors of each other, what are they?
They are all parallel
What are the i and j vectors?
i is a unit vector along the x-axis
j is a unit vector along the y-axis
If you have two vectors, for example 3i and 4j, how do you find its magnitude?
You ‘pythagorise it’
square both values and square root the sum
sqr root (9 + 16) = 5
Where do position vectors originate from?
(0,0), normally represented as O
