# Warm-Up Exercise for lecture 3

## Due 8:00 am, Tues, Sep 9

Physics 105, Fall 2008

T/F: Vectors are commutative (that is **A** + **B** = **B** + **A**)

☑ true

☐ false

To get the magnitude of a vector, you
should:

☐ add the magnitudes of its components

☑ take the square root of the sum of the squares
of its components

☐ none of the above

A car going 30 m/s
approaches a truck going 10 m/s in the opposite direction. The gap between the two
of them:

☐ remains constant

☐ closes at 20 m/s

☑ closes at 40 m/s

Briefly describe how you
would go about adding two vectors together using a ruler and protractor:

Draw the first vector as an error from the origin, pointing the proper angle, with the length proportional to the magnitude of the vector. Draw the second vector beginning at the end of the first vector. Point it the proper angle (relative to the axes, not relative to the first vector), and make its length also proportional to its magnitude. Then draw in the sum: an arrow going from the start of the first vector to the end of the second vector.

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