forces and motion Flashcards
what is the difference between speed and velocity
velocity measures direction
what are the two formulas for acceleration
a = (v-u) / t
v2 = u2 + 2as (v2 is v squared)
distance-time graphs what is a) gradient b)horizontal flat line c) sloped straight line d) curve
a) gradient = speed
b) flat = no movement
c) straight slope = constant speed
d) curve = acceleration or deceleration
velocity time graphs what is a) gradient b)horizontal flat line c) sloped straight line d) curve e) area
a) gradient = acceleration
b) flat = steady speed
c) straight slope = constant acceleration
d) curve = changing acceleration
e) area = distance
weight mass and gravity
W= mg
what is gravity/ weight
a force which acts straight downwards
what is a reaction force
a force which acts perpendicular and away from a surface
what is an electrostatic force
a force between two charged objects
what is drag/ air resistance/ friction
a force which slows something down
how to reduce friction
lubricant eg water, oil, grease
what happens to friction as speed increases
friction increases
newton’s first law of motion
balanced forces mean no change in velocity
newton’s second law of motion
if there is an unbalanced force (a resultant force) then the object will accelerate in that direction
force mass and acceleration formula
F = ma
vectors vs scalars
vectors measure direction and size; scalars only measure size.
vectors: force, velocity, acceleration, momentum
scalars: mass, temperature, time, length
why do objects reach terminal velocity
The object has weight so as it falls it accelerates
There is a drag force acting upwards
As the speed increases, the drag increases
Eventually drag=weight
Constant velocity due to balanced forces
( resultant force=0)
what is Hooke’s law
the extension is proportional to force
what is elastic behaviour
returning to original shape once the forces are removed
what is the elastic limit
the point past which the material no longer obeys Hooke’s law and will no longer return to its original shape
what affects thinking distance
how fast you're going reaction time ( influenced by tiredness, drugs, alcohol etc)
what affects braking distance
how fast you’re going
mass of vehicle
friction (road surface, weather, tyres)
how good your brakes are
