PreAP Due 10/2 - Tues

Do online homework 8. (If the online homework stops working - do this version.) We just checked and it's there, now!

Help -

1) Even though these questions are about "relative motion", they are just more adding of vectors. Don't let the new situations trick you. There is an example in Teacher Notes/ Two Dimensional Motion.

2) Here's an example of how this all works. Imagine you are walking in an airport. Let's assume you can walk 1 m/s in any direction. Let's assume that a moving sidewalk moves at 3 m/s to the right (positive). If you are walking on the sidewalk to the right, then V1 + V2 = 1m/s + 3 m/s = 4 m/s to the right. If you walked to the left on the sidewalk (the "wrong" way), then -V1 + V2 = -1m/s + 3 m/s = +2 m/s. To a person standing still on the ground next to the walkway, you would still be moving to the right at 2m/s.

If you are asked to calculate with these vectors - do the vector addition first, then the calculation with the resultant. In the first example (you walking with the sidewalk) Vtotal = 4 m/s. If you are given either a distance OR a time you could calculate the other, since V = X/T.

3) If the vectors are at angles, then you will have to do the entire vector addition process: resolve into components, find total x and y, find resultant, blah, blah, blah.

Come in for help if you don't get it. No excuses!

4) X and Y are independent of each other. Thought experiment (we'll do this tomorrow) - Imagine a little car that moves with constant velocity in the y-direction (from next to your body to away from your body). You put the object on a moveable piece of wood (like a large board). It takes the car 4 seconds to move from the bottom of the board to the top of the board. If you move the board to the right (x-direction) while you let the car move in the y-direction, the car will STILL take 4 seconds to move up the board. This proves that x and y do not affect one another.

Now, if you moved the board up and to the right, the "up" part is an y velocity and will add to the car's vertical velocity.

5) On the escalator problem - Be sure you understand relative motion from my notes here: man walking on flatbed truck: link here.

Then, if you know the length of the escalator is constant, it is relatively simple to solve.