Forces and motion: Forces in action Flashcards
what is the equation that links force to its acceleration
F=ma
how is weight defined
W= mg where g is the value of acceleration of freefall on the planetary body
define centre of mass
the point in space of an object where the mass of the object is seen to act through
define centre of gravity
the point in space of an object where gravitational forces are seen to act through
how do you find the centre of gravity for a non unform shape
hang the shape you want to determine the cenre of mass for off a clamp stand along with a plumb line, release the shape from one of the vertexes and let it fall under its own weight. draw a line going through the verex along the plumb line. repeat this process for a second vertex of the shape and the point in which the drawn lines cross will be the centre fo gravity
define weight
The gravitational force acting on an object through its centre of mass
define friction
a force that arises when 2 non smooth surfaces rub against each other
define drag
the resistive force on an object travelling through a fluid
define tension
the force within a stratched cable or rope
define upthrust
an upward buoyant force acting on an object when it is in a fluid equal to the weight of water displaces
define the normal contact force
a force arising when on object rests against another object (as a result of Newtons 3rd law of motion)
what is true of an object when it reaches terminal velocity
Resultant force acting on the object is 0 => the object is not accelerating anymore
define the moment of a force
the moment of a force is the turning effect of a force around some axis and is equal to force x perpendicular distance of the line of action of force from the axis or point of rotation
what is the principle of moments
for a body to be in rotational equilibrium, the sum of the anticlockwise moments about any point is equal to the sum of clockwise moments around that same point
when determining in a body is in equilibrium what 2 thing do you need to check
Resultant force = 0
resultant moment =0
define a couple
pair of equal and opposite coplanar forces that acts to produce rotation only
define the torque of a couple
one of the forces x the perpendicular separation between them
define density
the density of a subject is defined as its mass per unit volume p=m/v
how do you determine density for a uniform solid
use a high accuracy mass balance to determine the mass of the solid and take measurements using a ruler or micrometer to determine the value for the volume and use the denisity formulae to detemrien its desinty
how do you determine density for a uniform solid
use a high accuracy mass balance to determine the mass of the solid and determine the volume of the object using a eureka can and use the density formulae to determine its density
what is the equation of pressure
Pressure = force/area
how do you calculat the pressure exerted by a vertical column of any liquid from its weight and CSA
p=hρg
where h is the height of the liquid column
ρ is the density of the liquid and g is the acceleration of freefall
what is the equation for the upthrust on an object
Upthrust = Axρg where the volume of the block is Ax
ρ is the density of the object and g is the acceleration due to freefall
what is Archimedes’ principle
The upthrust exerted on a body immersed in a fluid is equal to the weight of the fluid it displaces
