ch 3 - dynamics Flashcards
resultant force =
resultant force = mass * acceleration
F = ma
newton’s second law?
. resultant force is proportional or equal to mass*acceleration
. resultant force is proportional or equal to rate of change of momentum of the body
what is intertia?
the tendency of an object in motion to remain in motion and object at rest to stay unless an external unbalanced force acts on it
a measure of how difficult it is to change the velocity or speed and direction of an object
measure of mass of an object
greater mass = greater inertia
acceleration inversely proportional to mass
what is weight?
the force on an object caused by a gravitational field acting on its mass, doenwards arrow
what is friction?
the name for a resistive force when two surfaces are in contact and tending to silde over one another, acts along a surface
what is drag?
a resistive force similar to friction, opposes the motion of the object in both air and water, reduced by giving object a streamlined shape
what is upthrust?
the upwards forces experienced by any object in the fluid, arises from pressure fluid exerts on an object
deeper = more pressure
if upthrust > object weight, objecy floats
what is a contact force/normal force?
a force that pushes up against you weight and give support so you don’t fall down
force than acts at right angles to the surface when two objects meet
what is tension?
the force in a rope or string when it is stretched, pulls back to shorten the string or spring
what is centre of gravity?
the point where the entire weight of an object appears to act
W = mg
g moon =
1.6 m s-2
g earth =
9.81 m s - 2
newton’s first law?
an object remains at rest or travels at constant velocity unless it is acted on by a resultant force
F = ma
uniform motion?
the natural state of motion of an object - uniform velocity, constant speed and direction
what is a resultant force?
the single force that has the same effect as all of the forces acting on the object
what is terminal velocity?
the maximum velocity reached by an object falling under gravity or accelerated by a constant force
what is a resistive force?
a backwards force in the opposite direction to movement caused by friction or some other viscous force
less drag in air because…
air less dense than water
newton’s third law?
whne two bodies interact, the forces they exert on each other are equal in size and opposite in direction
what are the characteristics of the forces that make a up a ‘newton’s third law pair’
. act on different objects
. opposite in direction
. equal in magnitude
. forces of the same type
forces of the same type can be:
. gravitational forces
. electrical forces
. contact forces
. tension forces
. magnetic forces
what are base units?
defined units of the SI system from which all other units are derived
. length = m
. mass = kg
. time = s
. electric current = A
. thermodynamic temperature = K
. amount of substance = mol
. luminous intensity = cd (candela)
what are derived units?
unit that are combinations of the base units of then SI system
force = (unit )
kg m s-2
speed = (unit)
ms - 1
what does homogeneous mean?
equations with the same base unit on each side are homogenous
kilo
10³ (k)
mega
10^6 (M)
giga
10^9 (G)
tera
10^12 (T)
deci
10^-1 (d)
centi
10^-2 (c)
milli
10^-3 (m)
micro
10^-6 (u)
nano
10^-9 (n)
pico
10^-12 (p)
