Proportions (aka Scaled diagrams)

https://www.youtube.com/watch?v=WXDoglJXKaY -

How to video

Announcements

MAKE SURE YOU BRING A RULER AND PROTRACTOR TO THE REGENTS

Practice

These types of questions are worth 5% of your regents grade. Please finish it at home

Determine the scale used• First, measure one of the vectors in cm

• Then, set up a proportion:

X/1cm = 1.5/7.5cm

[1 cm = 0.233m/s]

• Double check your work by making sure that your scale works for the other vector in the picture

Drawing the resultant• Set the vectors up in tip-to-tail and then draw the

resultant (use a ruler to redraw the vector)

Resultant

Picture you are given

Picture you need to set up

Shorcut: As long as you drew the scaled vectors

correctly, you can just measure the resultant

with your ruler

Pythagorean theorem: a^2 + b^2 = c^2 0.7m/s^2 + 1.5m/s^2 = c^2

c = 1.66 m/s

angle?

Shortcut: You can just measure the angle with your protractor!

angle?

Notice: tan(ø) = opp/adj Therefore: tan(ø) = b/a

tan(ø) = 0.7/1.5 ø = tan^-1 (0.7/1.5)

ø = 25º

NOT DONE YET!

The question is asking for the angle between NORTH and the resultant velocity, not just the angle.

So the actual answer is 90º - ø

= 90º - 25º = 65º

If you need to, refer to this powerpoint as you

work through the practice set (it is posted

online along with the answer key)

Giving back exams