Kinematics
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What is Kinematics?
the branch of physics describing motion
What is distance?
how far an object has travelled
What is time?
how long it takes for an object to travel
What is speed?
the rate of change of an object’s position
What is scalar quantity?
a quantity that has size but no direction e.g. speed, time, distance
What is a vector quantity?
a quantity with both size and direction e.g. displacement, velocity, acceleration
What is displacement?
the change in position of an object, with direction
What is velocity?
speed of an object in a certain direction
How to calculate distance?
speed x time
How to calculate time?
distance / speed
How to calculate speed?
distance / time distance travelled —————————- or time taken d2 - d1 s (average) = ---------------- t2 - t1
What is average speed?
the average of instantaneous speeds over a period of time
What is instantaneous speed?
how fast an object is moving in a single moment
What does the gradient of a distance-time graph give?
speed
What does the gradient of a speed-time graph give?
acceleration
How to find distance travelled on a speed-time graph?
find area beneath speed-time graph gradient
What is acceleration?
• a change in velocity i.e. speeding up, slowing down, changing direction
What unit is used for acceleration?
m/s/s or m/s^2 (squared)
What is an increase in velocity called?
positive acceleration or acceleration
What is a decrease in velocity called?
negative acceleration or deceleration
How to calculate average acceleration?
change in velocity ——————————- or time taken to change final speed - initial speed v2 - v1 ————————————– —> a (average) = —————- final time - initial time t2 - t1
How to calculate average velocity?
time
What does the gradient of a velocity-time graph give?
acceleration in a direction
If positive and negative directions are not defined…
positive acceleration means getting faster and negative acceleration means slowing down