Carefully look at they axis to
¢V know what you are calculating.
a=
¢t Acceleration or speed
r
Velocity time graphs
To determine instantaneous
Displacement time graphs velocity draw a tangent at a
Displacement is plotted on the y axis seven time and work out
time is plotted on the x axis the gradient
Stationary
Constant velocity
Returning at a constant velocity
,Area under the graph
Area under the graph is equal to
displacement
Equations of motion
You need four equations to calculate quantities involving motion in a
straight line at a constant acceleration.these are known as the suvat
equations
Equation without s
v = u + at
Equation without v
1
S = ut + at2
2
Equation without A Equation without T
1
S = (u + v) t v 2 = u2 + 2as
2
,Average speed
Average speed = distance travelled
¢x
v=
Time taken ¢t
Displacement and velocity
Average velocity = change in displacement ¢S
V =
Time ¢t
Distance time graphs
Distance is plotted on the y axis
a
Time is plotted on the x axis
Speed is the gradient of the distance time graph
Instantaneous speed
Instantaneous speed is the speed over a very short interval of time
and is found by drawing a tangent at that time on a speed time graph
,Car stopping distances
a Thinking distance, the distance travelled between the moment when
you first see the reason to stop, to the moment when you use the
brake
Braking distance, the distance travelled from the time the
brake is applied until the vehicle stops
Many factors influence these distances:
Speed of vehicle
Condition of brakes, tires and road
The alertness of driver
Thinking distance = speed x reaction
D t / tr
, Free fall and G Acceleration due to gravity
The acceleration of free fall is
The value for g varies upon known as g
altitude and latitude but it is When an object accelerates
generally 9:81ms ¡2
under gravity with no other force
it is said to be in free fall
Determining g can be done by dropping a ball over a known
distance and liming its decent. However, It happens very quickly
so there is other ways to measure it
Electromagnet trapdoor
When the current is turned of a timer is
triggered and the magnet demagnetises
and the ball falls. When the ball hits the
trapdoor the contact is broken and the
timer stops
Light gates
There are two light gates and when the ball falls through the first
beam it interrupts the light and the timer starts. When the ball passes
through the second beam a known distance further down the timer
stops