Test on Motion - Grade 9 Flashcards
Actual Speed
The distance traveled by body at particular instant of time
Speed
The average speed of an object is given by the ratio between distance travelled (usually in meters) and the time taken (usually seconds).
Distance/time
Units for Speed
Kilometers per hours (km/h)
meters per second (m/s)
miles per hour (mph)
Magic Triangle
d = t x v
v = d / t
t = d / v
Velocity
Speed with direction
Scalar
A quantity that is represented by a simple numerical value.
Example: mass, temperature, time
Vector
A quantity that has a value (magnitude) as well as a direction.
Example: force, weight, velocity
Acceleration
Occurs when there is a change in speed, or direction, or both = when there is a change of velocity.
Negative or positive
Vector
When speed increases
positive acceleration
When speed decreases
negative acceleration
When changing direction…
speed is not changing
but
velocity is changing
Find the final speed
Initial speed is zero: v = a x t
Initial speed is not zero: v = u + (a x t)
Acceleration equation
(v - u) / t = a
Acceleration symbol
acceleration = a
Speeding up
Slowing down
Changing direction
Distance time graph
horizontal line = no movement
line going up = positive constant speed
line going down = negative constant speed
curved line going up = positive acceleration
curved line going down = negative acceleration
how to find the speed in a distance time graph
rise over run
distance over time
The slope in a distance time graph
the slope (gradient) of a line is numerically equal to the spread
the slope in a speed time graph
the slope (gradient) of a line is numerically equal to the acceleration
Speed time graph
horizontal line on the x axis = no movement
horizontal on pos. side = positive constant speed
horizontal on neg. side = constant negative speed
line going up = positive acceleration
line going down = negative acceleration
To find the distance travelled
the area under the line is equal to the distance travelled
d = v x t
example: 10 x 15 = 150
find the area of the section
if it is a triangle than divide by 2
Falling under gravity
When released any object will fall with increasing speed; acceleration
Object fall because of the force of gravity
The shape is more important than the weight because of air resistance
Acceleration of free fall
without air resistance all objets will fall with the same acceleration, known as the acceleration of free fall or g
each the value is: g = 9.80665 ms -squared
Motion under free fall
if an object is moving under free fall its velocity is given by: v = g x t
10t
the distance: d = 1/2 g time(squared)
5t squared
