Physics test 9th grade #1 Flashcards
Speed formula
distance/time
Speed definition
The speed of an object is given by the ratio between distance travelled and time taken
Are average speed and actual speed the same
No, actual speed changes while average speed does not
how is speed measured
Km/h
m/s
mph
What is the magic triangle
Distance/speed x time
How fast
speed - distance/time
how far
distance - speed x times
how long
time - distance/speed
difference between speed and velocity
speed is about movement in general while velocity is speed with direction
Vector
A quantity that has value (magnitude) as well as a direction. Number + Unit + direction
Scalar
A quantity that is represented by a simple numerical value. Number + unit
is velocity is vector or scalar
vector
Is speed a vector or scalar
Scalar
What symbol is used to represent velocity?
an arrow.
is weight a scalar is vector or scalar
weight is a vector
is acceleration a vector or scalar
vector
What do the details that the symbol that represents velocity tell us
Length = magnitude/size
Direction = direction
What is acceleration
when there is a change in velocity:
- speed increases (positive acceleration)
- speed decreases (negative acceleration)
- change in direction
When acceleration occur
when there is a change of speed, direction, or both
acceleration formula
a = (v - u) / t
a = acceleration
u = initial speed
t = time
When speed increases it is called
positive acceleration
when speed decreases its called
negative acceleration
In distance time graphs, whats on the x axis and whats on the y axis
distance is on the y axis, time is on the x
In a distance time graph, a straight flat line represents…
no movement (v=0)
In a distance time graph, positive constant speed is show as…
a straight line going vertically up
In a distance time graph, if there are two lines, how do you determine which one is greater
look at the distance both lines are at at the same time to determine which one is greater
In a distance time graph, how do u represent negative constant speed
a straight line going down
How do you show acceleration on a distance time graph
it is a slope. Negative goes down and positive goes up
What is the formula to find the slope
rise/run
In a distance time graph, are the slope and speed related
yes, mathematically speaking, the slope is the speed because rise/run = distance/time
In speed time graphs, what does no movement look like
a straight line on the x axis
In speed time graphs, what does constant positive speed look like
A straight line not on the x axis
In speed time graphs, how is negative speed represented
by a line under the x axis
In speed time graphs, what does a diagonal line going up represent
positive acceleration
In speed time graphs, what does a diagonal line going down represent
negative acceleration
In speed time graphs, how to you determine which line is greater
whichever is higher up
In speed time graphs, what is the slope equivalent to
acceleration.
slope = rise/run = speed/time
acceleration = speed/time = rise/run
How do you find the distance on speed time graphs?
Find the area of the shape made by the line. For a rectangle it would be speed x time. For a triangle it would be 1/2 speed x time
What happens to an object after its released
it falls with increasing speed which is acceleration
Why do objects fall
gravity
when do heavier objects fall faster than lighter ones
when theres air resistance
what 2 forces act upon an object
gravity and air resistance
what affects air resistance
the shape of the object
If there was no air resistance, how would this affect objects
all objects would fall with the same acceleration. This is called the acceleration of free fall or g
the speed at which an object falls in a vacuum depends on…
the local gravitational field strength
What does g stand for
the acceleration of free fall
What is the acceleration of free fall
The acceleration of objects falling without air resistance
What is the g on Earth
approximately 10
Will an object fall faster on the moon or earth (with no air resistance)
The earth because it has a stronger gravitational field than the moon does
If an object is moving under free fall, its velocity is given by
v = g x t
or
v = 10t
How do you find the distance of an object that is accelerating free falling
5t^2 where t = time
This is because normally you would do 1/2 speed x time. Speed is 10t. so it is 1/2 10t x t. This can be simplified to 5t^2
What is free fall
falling because of the force of gravity without air resistance
if a rock fell for 3 seconds what would be its velocity and distance travelled
v = 30
d = 45m
what is free fall?
anything that is released into the air. For example, even throwing something up is considered free fall
How do you find velocity and distance when an object is launched straight up in the air (free fall)
as the object moves up, the velocity decreases by ten. as it goes down, it repeats the sequence in reverse (increases by 10)
If an arrow was shot straight up for two seconds at an initial speed of 20, what is its velocity every second
t = 0 v = 20
t = 1 v = 10
t = 2 v = 0
t = 3 v = 10
t = 4 v = 20
How do you find the distance of an object in free fall when its shot up straight in the air
the total time squared times 5.
For example, 4 x 4 = 16. 16 x 5 = 80
Newtons first law
an object in motion will stay in motion unless another force acts upon it
Newtons third law
for every action, there is an equal and opposite reaction
force formula
force = acceleration x mass
how to draw a force diagram
four arrows showing four forces
- earth pushing up
- gravity
- friction/ air resistance
- momentum from vehicle
resultant force: bigger force - smaller force
mass vs weight
Mass is the total amount of matter, or “stuff,” in an object. Weight is the force of gravity on an object.
w = mass x 10
