When you have multiple choice, the longest ones are usually made up.
To do: practice 2.5.1, 2.6.1 → at physicslab
also read chapter 3
What are the goals of science?
Betterment of life.
For competition.
Satisfying curiosity.
Looking for truth.
Explaining and predicting.
Adapt existentially to changes.
→
Explain, Describe, Predict, Apply.
Science is about patterns, and furthermore about distinguishing the principles behind those patterns, which in term explain the patterns.
Kinemetatics represents description in physics.
And the explanatory principles to kinematics, is dynamics.
To explain the change that happens in kinematics, we use vectors and calculus.
And only with these tools can we actually do dynamics.
Kinematics
The study of motion: from greek kinon, meaning motion.
We use vectors to describe the position of an object, its displacement, velocity, and acceleration.
Vectors were not known during Newton’s time, but they are more or less indispensible now a days.
Vectors are important for all of math.
A vector is a quantity that has both magnitude and direction. It is typically represented symbolically by an arrow in the proper direction, whose length is proportional the magnitude of the vector.
Even though a vector has magnitude and direction, it does not have a fixed position. A vector is not altered if it is displaced parallel ot itself, as long as its length and orientation are not changed.
In print: represented by boldface letter. eg.. r, v, or a. (or on paper, arrows)
Position vector: tells us where something is relative to an origin.
The length of the vector tells us the distance from the point to the origin.
Remember to always add units in physics.
Three other relevant vectors:
Displacement vectors
[velocity vectors
acceleration vectors]
These two require vector operations.
Every operation needs to be freshly defined for vectors, compared to scalar quantities.
Division by vector is not meaningful.
If vector a is added to vector b, the result is another vector, c, written a + b = c. The operation is performed by displacing b so that it begins where a ends. C is then the vector that starts where a begins and ends where b ends.
The sum of the two vectors can be found by the parallelogram method.
A particle moving with constant volocity v suffers a displacement s in time t given by s=vt. The vector v has been multiplied by the scalar t to give a new vector, s, which has the same direction as v but cannot be compared to v in magnitude (a displacement of 1m is neither bigger nor smaller than a velocity of 1m/s).