Kimematics is the study of motion. Kinos (from Greek) means movement. The word cinema comes from kinema (moving images). Kino means cinema in German.
Uniform motion, as the name implies, occur at constant speed. The velkocity is given by the distance travelled divided by time:
$$\begin{aligned} \mathrm{v = \frac {s}{t}} \end{aligned}$$
The formula above is so simple that it is not included in the IB physicas data booklet. Only the formulas for accelerated motion (next topic) are.
Notice that this formul rearranges to
$$\begin{aligned} \mathrm{s = vt} \end{aligned}$$
Which is ananlogous to the equation for a straight line (in maths) but with s instead ofy and t instead of x. That means that we can apply this branch of maths to physics, including the graphs. If you know the maths, the physics gets much easier..The higher the incline of the line graph, the higher the velocity.
Example calculation
1) If you travel from Brighton to London (50 miles) in 1 hour, what is your (average) velocity?
v = 50 miles / 1 hour = 50 miles / hour
2) If I travel at 100 miles an hour for 3 hours, how far do I get?
s = 100 * 3 = 300 miles
The units
We normally use SI units (m,s,m/s) but sometimes we get questions in km per hour, or miles (like in the examples above) and we may have to change from m/s to km/s.
Average speed
The speed may change during the motion. To make things easier we introduce the concept of average speed, which is the total distance travelled divided by the time taken.
Example 1: If we travel from Brighton to London in 1h the average speed is 50 miles/h . It doesn´t mean that we have been at this speed all the time: usually thare are parts of the journey you move slower and others you move fast. You may even stop for coffee. The average speed is a useful concept nevertheless.
Example 2: The speed of the Earth mopvcing around the Sun is an average speed. Because Earth´s orbit is not perfectly circular, the velocity increases when closwer to the Sun.
The difference between speed and velocity
The velocity is different from speed because it is a vector wauntity,so that it has a direction (usually repreented by an arrow) in addition to the speed. Look at the vector section for more on the difference between speed and velocity.
TOK - theory of knowledge
By using the formulas of kinematics we are able to calculate the position of objects at any point in the future. This gave rise to mechanicist theories which claim that th euniverse works like a clock and its future is determined.This has also repligious implications, like the ideas of freewill.
Because living beings and all other stuff in the Universe are madeof particle, and we can use kinematics track and predict the motion nof all these particles, we can in pronciple predict the future. IN practice this is not possible because of the large number of particles involved.
However, moden physics showed that the behaviour of very small particles, like atoms and molecules, cannot be exactly predicted like is the case for macroscopic objects, and an statistical theory is needed. Still, modern physics allowed for the development of the electronics industry and much more.