# Warm-Up Exercise for lecture 3

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

Physics 105, Fall 2009

T/F: It doesn't matter which order you add two vectors together, you will get
the same sum either way.

☑ true

☐ false

Which geometrical shape does a 2D
projectile follow?

☐ line

☐ circle

☐ ellipse

☑ parabola

☐ hyperbola

A man on a treadmill is walking at
1.5 m/s to the left. The treadmill is going at 2 m/s to the right. If you are
standing still, it looks like the man is moving:

☐ 0.5 m/s left

☐ 3.5 m/s left

☐ stationary

☑ 0.5 m/s right

☐ 3.5 m/s right

Ralph is confused about how his book defined the components of a vector. The
book says, "The components of a vector are the projections of the vector along
the coordinate axes". What can you tell Ralph to help him understand what this
means?

Think of shining a light perpendicularly towards an axis, with the arrow blocking the light beam. The "projection" of the arrow is just the shadow the arrow creates on the axis.

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