Forces, Pressure and Dencity Flashcards
what is the center of gravity? (C.o.G)
it is the point at which the weight of an object may be considered to act
what is meant by stability?
weather a object will or will not topple (fall over)
what is the difference between C.o.G and C.o.M?
Center of gravity depends on the gravitational field
Center of mass does NOT depend on the gravitational field
what is a moment?
the turning effect of a force?
define moment or turning effect
moment = Force X perpendicular distance from the line of action to the pivot
define equilibrium of an object
when an object is stationary or moving at a constant velocity.
aka: Resultant Force on the object = 0
define rotational equilibrium
the net moment = 0
or
clockwise moment = anti-clockwise moment
what is the definition of force
the rate of change of momentum
true or false acceleration of free fall is not dependent on mass
True
define Pressure
Force per unit area
p = F/A
what is atmospheric pressure?
101 325pa or 101.325kpa
define density
mass per unit volume
roh = m/V
what is hydrostatic pressure?
the pressure that is exerted by a fluid at a given point within the fluid due to the force of gravity
what is the formula to calculate hydrostatic pressure?
p = (roh) (g) (delta h)
where:
p = pressure
roh = density
g = the acceleration of gravity
h = hight of object
what is archimedes principle?
an object submerged in a fluid has an upward buoyancy equal to the weight of the fluid displaced by the object
True or false an object will float when the upthrust = weight of object
True
define a couple
a pair of forces (of equal magnitude) acting in opposite directions that only produce rotation
true or false a couple depends on a pivot
false
what do you call the moment of a couple
Torque
how do you calculate Torque (moment of a cople)
Force X Distance between forces
can the forces in a couple share the same line of action?
no
define upthrust (buoyancy force)
a force that pushed upwards on an object submerged in a fluid
what causes upthrust?
a difference in hydrostatic pressure at the top and bottom of an object
state the law of moments
for an object to be in equilibrium the clockwise moment must equal the anticlockwise moment
what is the formula for a moment?
Force X perpendicular distance
