Kinematics is the study of motion, or more correctly, the analysis and measurement of motion.
In the series of lessons we are going to examine some aspects of motion in one dimension.
But before we start it maybe useful to see where kinematics sits in the context of classical mechanics.
The following video gives you an introduction to the concept of mechanics tying in not only kinematics, which is the analysis of motion but also dynamics which is the analysis of the cause of motion.
In the series of lessons we are going to examine some aspects of motion in one dimension.
But before we start it maybe useful to see where kinematics sits in the context of classical mechanics.
The following video gives you an introduction to the concept of mechanics tying in not only kinematics, which is the analysis of motion but also dynamics which is the analysis of the cause of motion.
This next video provides an overview of kinematics, and introduces some key terms such as distance and displacement, speed and velocity, and how they relate. A good start before you get into the specifics of kinematics.
3. Acceleration
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worked solution
going deeper
problems
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Coming soon
worked solution
coming soon
going deeper
What does a cereal have to with motion? Well read on....
There are a number of ways we can explore this concepts further.
One aspect of most high school physics course on kinematics, is that they only concern themselves with constant acceleration. In reality however, acceleration, like displacement and velocity, can change with respect to time.
Velocity is the rate of change of displacement. Unit: m/s2
Acceleration is the rate of change of velocity.
So what is the rate of change of acceleration?
The answer to that is the jerk. So slope of the acceleration vs time graph is the jerk. Unit: m/s3
We can go further.
What is the rate of change of the jerk?
Well it's the snap. Unit: m/s4
Can we go further? Yep. The rate of change of snap is the crackle. Unit: m/s5
I think you can guess the next one.
problems
coming soon
4. Graphing Motion
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In this video, I use the animations from pHET I explain the graphs generated from three times of motion, stationary, constant velocity and constant acceleration. I also discuss how you can determine variables such as velocity displacement and acceleration from these graphs. Click the TAB to see a sample question for you to try, which I then provide a was of solving it. There also some great interactive for you to play with. See the TAB |
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Graphs allows to visualise what is occurring in terms of motion. However we can also use the graphs as a mathematical way to establish mathematical models or equations. So we can derive equations of motion from graphs of motion.
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interactives
Explore different kinematics graphs with this Geogebra interactive by Tom Walsh
- pHET graphing animation - this interactive from the University of Colorado pHet team is a great way to demonstrate the relationship between motion and its graphical analysis. That why I used it in my video. At this time its Java based so will only work on PC/Mac
- Walter Fendt interactive on motion graphs - another good simulation and is HTML5 based so will work on all devices
worksheets
These I have collected from a variety of places.
5. Equations of Motion
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There are relationships between each of the variables involved in kinematics and these mathematical relationships are modeled in what are know as the kinematic equations, or equations of motion. This video covers the 5 forms of kinetic equations and how they are derived.
Click the 'going deeper" tab in "4. Graphing Motion" to see how they can be derived from the motion graphs. See the worked solution tab if you want a demonstration of a kinematic problem using equations of motion |
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It is always helpful to attempt the problem first before looking at the sample solution
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problems
- A car travel 20 km at 40 km/h. What speed should the car cover the next 20 km to have an average speed of 60 km/h for the whole journey? (120km/h)
- A car leaves place at 8 am and Travel at 60 km/h. Another car leaves the same place at 8:30 am and I was at 80 km/h. When and where will the second car overtake the first car? (10am, 120km)
- An aircraft needs to reach a speed of 80 m/s before it can take off. If it accelerates at 3 m/s2, calculate the length of the run by used. (1070m)
- And object moving with a constant acceleration can certainly slow down. But can an object ever come to a permanent halt if it’s acceleration truly remains constant? Explain.
- A car with his brakes full on decelerates at 4 m/s/s. If the car is moving uniformly at 20 m/s when a cow crosses 60 m in front of it, and if it takes a car six seconds to come to rest calculate how long it took the driver to apply the brakes. Does it hit the cow? (1 sec, yes they hit the cow)
