chapter 8: Flashcards
8.1: what is mechanics?
deals with motion and the action of forces on objects
8.2: what is a particle? (modelling assumption)
dimensions of the object are negligible
8.2: what is the modelling assumption of particles?
1) mass of object is concentrated at the single point
2) rotational forces and air resistance is ignored
8.2: what is a rod? (modelling assumption)
all dimensions but one are negligible, e.g beam or pole
8.2: what are the modelling assumption of rods?
1) mass is concentrated on a line
2) no thickness
3) rigid (does not bend or buckle)
8.2: what is a lamina? (modelling assumption)
object with an area, but negligible thickness, e.g paper
8.2: what are the modelling assumption of lamina?
mass which is distrubuted along a flat surface
8.2: what is an uniform body? (modelling assumption)
mass which is distrubuted evenly
8.2: what are the modelling assumption of an uniform body?
mass of the object is concentrated at a single point at the centre of the body. CENTRE OF MASS
8.2: what is a light object? (modelling assumption)
mass of the object is smaller compared to other masses. e.g, string or pulley
8.2: what are the modelling assumptions of a light object?
1) treating the object of having zero mass
2) tension is the same at both ends of the light string
8.2: what is an Inextensible string? (modelling assumption)
a string that does not stretch under load
8.2: what are the modelling assumptions of an inextensible string?
the acceleration is the same in objects connected by a taut inextensible string
8.2: what is a smooth surface? (modelling assumptions)
the surface with no rugosity, so friction is negligible.
8.2: what are the modelling assumptions of a smooth surface?
assuming that there is no friction between the surface and any object on it
8.2: what is a rough surface? (modelling assumptions)
if a surface is not smooth, it is rough
8.2: what are the modelling assumptions of a rough surface?
if objects are in contact with the surface experience by a frictional force if they are moving or acted by a force.
8.2: what is a wire? (modelling assumption)
rigid thin length of wire
8.2: what are the modelling assumptions of a length of metal?
treated as a one dimensional
8.2: what is a smooth/light pulley? (modelling assumption)
all pulleys you consider will be smooth and light
8.2: what are the modelling assumptions of a smooth/light pulley?
1) pulley as no mass
2) tension is the same on either side of the pulley
8.2: what is a bead? (modelling assumption)
particle with a hole for threading on a wire or string
8.2: what are the modelling assumptions of a bead?
1) moves freely along a wire or string
2) tension is the same on either side of the bead
8.2: what is a peg? (modelling assumption)
a support where a body can be suspended or rested
8.2: what are the modelling assumptions of a peg?
1) dimensionless and fixed
2) can be rough or smooth
8.2: what is air resistance? (modelling assumption)
resistance experienced as an object moves across the air
8.2: what are the modelling assumptions of air resistance?
using modelled of negligible
8.2: what is gravity? (modelling assumption)
the force of attraction between all objects. gravity = 9.8ms^-2
8.2: what are the modelling assumptions of gravity?
1) assuming that all objects with mass are attracted towards the earth.
2) earths gravity is uniform and acts downwards
3) g is constant and is 9.8ms^-2
8.3: three types of SI units?
1) mass (kg)
2) length (m)
3) time (sec)
8.4: what is a vector?
is a quantity which has both magnitude and direction
8.4: name an example of a vector
1) displacement (m) - (distance in a direction)
2) velocity (m s^−1) - rate of change of displacement
3) acceleration (m s^−2) - rate of change of velocity
4) force (N)- described by a magnitude, direction and point of direction
8.4: what is a scalar?
only has magnitude
8.4: what are some examples of scalars?
1) distance (m) - measure of length
2) speed (m s^−1))- measure how quickly a body moves
3) time (sec) - measure of ongoing events taking place
4) mass (kg)- measure of the quantity of matter contained in an object.
8.4: are scalars positive or negative?
positive
8.4: are vectors positive or negative?
they can be both
