Kinematics is the study of moving objects and their distance and displacement, speed and velocity, acceleration, and time spent travelling.
There is a lot of relevance to everyday life. Just think about the journeys you take to and around school!
Here we'll define the key quantities and equations. Take care to learn what the symbols represent.
Distance (\(d\)) is the total length of the path taken. Displacement (\(s\)) is defined as the straight line distance between the start point and the final point. Note that an object moving through a complete circle has a distance equal to the circumference but a displacement of zero!
Speed and velocity have the same units, m s-1 , but speed is a scalar and velocity is a vector. Average speed is definied as the total distance divided by the total time. Velocty is defined as the rate of change of displacement, and is in the same direction as the change of displacement.
\(\text {speed} = {\text{distance}\over t}\)
\(\text {velocity} = {\text{displacement}\over t}\)
Acceleration (ms-2) is defined as the rate of change of velocity, so if velocity changes there must be acceleration.
\(\text{acceleration} ={ \text{change in velocity} \over t}\)
In 1-dimension, the sign tells us the direction of the vector.
You will usually choose right or upwards as the positive direction, but always consider what would be best in a given question.
The equations of uniformly accelerated motion are often referred to as "the suvat equations" as a convenient reminder of the symbols used to represent the key quantities in the motion that we will consider.
\(v=u+at\)
\(s={(v+u)\over 2} t\)
\(s=ut+{1\over 2 }at^2\)
\(v^2=u^2+2as\)
- \(s\) is displacement (m)
- \(u\) is initial velocity (m s-1)
- \(v\) is final velocty (m s-1)
- \(a\) is acceleration (m s-2)
- \(t\) is time (s)
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How much of Kinematics have you understood?
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