Introduction+and+Motion+Concepts

=Introduction to Physics=

What is Physics? - Universal Laws, Study of Energy (energy transformations and energy conservation) Unit 1 - Motion - Focus of unit - analyzing motion (calculations, graphs); describe how things move

1.Types of Motion

 * uniform motion in a straight line (constant speed and direction)
 * motion in more than one direction (2-dimensional)
 * accelerated motion - speeding up or slowing down

2.Calculations for Uniform Motion

 * distance, speed, time: v = d/t (rearrange to solve for d or t)
 * solve problems using relationships of d - v - t
 * MUST use consistent units (m, sec, m/sec), (km, hr, km/hr)
 * convert units to consistent form (ie: km/hr to m/sec - divide by 3.6)

Lab - Uniform Motion with a Ticker Timer Lab - Carts and Collisions

3. Scalars and Vectors
In physics we differentiate between quantities with directions and those without directions
 * scalars - have only size, no direction (ex: m/s, km)
 * vectors - have BOTH size and direction (ex: km/hr [North], m [SE])
 * Distance and Speed are both scalars, while Displacement and Velocity are both vectors
 * The difference between distance and displacement is the following: distance measures the actual path traveled, regardless of the route taken; displacement measures the SHORTEST distance between the starting and ending points.
 * It can easily be shown that displacement will always be less than or equal to the distance for any trip (unless the trip is in one direction only - in which case the two will be equal)
 * Velocity is the displacement divided by the time taken; velocity has a direction (since displacement also has a direction). Velocity will also be less than or equal to the speed for any trip.

4. Calculation of speed and velocity (for vector problems)

 * speed calculations have already been taught.
 * Velocity requires you to find the shortest distance between your start and end points - in many cases this will require work with angles.
 * Fortunately, most of the angles in problems for this course are 90 degrees, so we can use the Pythagorean theorem.
 * However, if the paths taken are not at right angles, you may be required to use the law of sines or law of cosines.

5. Average speed and average velocity (from graphs)

 * ave speed - find the length of the entire trip and divide by the total time
 * ave speed - method 2 - use the "weighted average" if the speeds are not for equal times
 * ave velocity - find the shortest distance from start to finish and divide by the total time
 * the slope of the line on a distance-time graph gives the speed for that section
 * a horizontal line has a slope of zero and thus a speed of zero.

6. Instantaneous speed (tangent method)

 * in cases where the speed is constant, the instantaneous speed is the slope of the dist-time line
 * in cases where the speed of an object changes over time, the graph is not likely to be a straight line
 * for curved dist-time graphs, we draw a tangent to the curve (just touches the curve at the point in question)
 * then we measure the slope of the line (rise/run, using the scales on the distance and time axes)
 * this method is only an approximation, but will have to do until you learn calculus.