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Objects in Motion :8ball: (Motion of a car (Speed (how fast the car is…
Objects in Motion :8ball:
Using SI units
International System of Units
Base units
ampere
A
electric current
kelvin
K
temperature
second
s
time
metre
m
length
kilogram
kg
mass
candela
cd
luminous intensity
mole
mol
amount of substance
Motion of a car
Distance
how far the car has travelled
the symbol for distance is
d
Displacement
the change in the car's position in terms of directino and distance
the symbol for displacement is
s
Speed
how fast the car is moving
= distance / time
average speed is the overall speed of the entire trip
instantaneous speed is the speed of the car during a given period of time (when the car is at a constant speed)
the symbol for speed is
S
Time
the amount of time from the start of the trip to a given moment during the trip
the symbol for time is
t
Velocity
the symbol for velocity is
v
= displacement / time
speed in a particular direction
average velocity is the overall velocity of the trip
instantaneous velocity is the speed of the car in a particular direction, during a given period of time
Acceleration
the rate at which the car is speeding up
the rate at which a car is slowing down is negative acceleration
change in speed / change in time
Speed measuring devices
Speedometer
measures travelling speed
drivers use it so that they can adjust their speed to be safe
RADAR
police use it to check for speeders
bounce sound waves off a moving object
LIDAR
police use it to check for speeders
bounce light waves off a moving object
Motion Graphs
Position-time
Speed-time
Newton's Laws
The Law of Inertia
an object will remain at rest or in constant motion in a straight line unless acted on by a net unbalanced force
inertia is the tendency of an object to resist changes in its motion while either at rest or in constant motion
A car stops abruptly, all the passengers will be inert and keep going forward, until a net unbalanced force (like a seatbelt) catches them
Newton's Second Law
the acceleration of an object is directly related to the magnitude and direction of the force acting on the object, and inversely related to the mass of the object
F = ma
Newton's Third Law
For every action force, there is an equal and opposite reaction force
The reaction force is often called the 'normal force'
Systematic and Random Errors