motion Flashcards
speed is
distance travelled per unit of time
average speed is
speed measured over a relatively long period of time
average spped equation
istantenous speed is
spped measured over an extremely short period of time
speed symbol
unit
v or u
m/s
distance symbol
unit
d metres (m)
time symbol and units
seconds t
time, speed, distance related by formula
d=vt
Velocity and speed differences
Velocity includes a direction (the direction of travel) as well as its value (its magnitude). vector
scalar speed only magnitude
velocity is
speed in a particular direction
Two objects can have equal speeds but might have opposite (if they are travelling in).
velocities
opposite directions
Acceleration is
the rate of change of velocity
how much the velocity of an object changes by every second.
Acceleration equation
acceleration units and symbol
a m/s2
maximum acceleration found by
choosing the part of the graph with the steepest gradient and calculating the gradient
A distance time graph shows how
the distance of an object (from a point) varies over time:
A horizontal line means
stationary, not moving
A straight line means
constant speed.
If the gradient increases
the object is speeding up (accelerating).
If the gradient decreases the object is
slowing down (decelerating).
If the line is going down, t
the object is moving backwards.
The speed of an object is given by the
in a distance time graph
gradient of the line.
Calculating Speed in a time-distance graph
Distance-time graphs are also known as
position-time graphs or displacement-time graphs
spped time graphs also known as
velocity-time graphs
A velocity-time graph shows how
the velocity (or speed) of an object changes over time.
If the line is horizontal, the velocity or speed is
constant (no acceleration).
v=0
If the line slopes upwards then the object is
accelerating (speeding up). constant
If the line goes down then the object
is decelerating (slowing down).
The distance travelled by an object can be found by
determining the area beneath the graph.
If the area beneath the graph forms a triangle (the object is accelerating or decelerating) then the area can be determined using the formula:
area = 1/2 x base x height
If the area beneath the graph is a rectangle (constant velocity) then the area can be determined using the formula:
area = base x height
The acceleration of an object is given by the gradient of the graph:
Lines that slope downwards have
negative gradients and so can be said to have negative accelerations: This is the same thing as a deceleration.
If the gradient of the line changes then the acceleration of the body must be changing:
A line with constant gradient represents constant acceleration (linear motion).
A curved line represents changing acceleration – either decreasing (if the gradient gets smaller) or increasing (if the gradient gets large).
DO QUESTION ON PAGE 11 IGCSE PHYSICS EXPLAINED AND SEE HOW IT WENT THERE
V=
when the initial speed is zero, formula can be expressed as v=
u+at
at
do problem page 13
do problem page 14
In the absence of air resistance, all objects fall with
…regardless of
he same acceleration, their mass.
This acceleration is equal to the…
approximately
So long as air resistance remains insignificant, the speed of a falling object will
gravitational field strength
10 m/s2 near the Earth’s surface.
increase at a steady rate, getting larger the longer it falls for.
in free fall, there is… acceleration
constant
when a object is dropped from an height and falls to the ground, the force acting on it causes it to fall is the ….
force due to gravity
When a parachutist jumps out of an aeroplane, two main forces act:
Weight (the force of gravity)
Air resistance
describe free fall
page 20
Initially the air resistance is very small. There is a downwards unbalanced force and the skydiver accelerates.
As the skydiver speeds up, the air resistance increases.
Eventually the air resistance balances the weight and so the skydiver travels at a constant speed – terminal velocity.
When the parachute is opened the increased air resistance on the parachute creates an upwards unbalanced force, making the parachute slow down.
an object thrown upwards decelerates at
10 m/s2
if there is sufficent air resistance, then the object’s acceleration starts at 10 m/s2 and then decrease to..
velocity becomes
called
zero
constant
terminal velocity
if a student drops two objects of different masses frokm the leaning tower, objects accelerate at … and …
10m/s2
hit the ground at the same time provided air resistance is negligible
if the student dropped a rock and a feather at the same time , feather would…
be more affected by air resistance and quickly reach termianl velocity
