AP Physics 1 - We Can Do This!

In every other class you've ever been in (with the exception of Pre-Calculus), everything has been a scalar value.  It's a number with units.  Here are some examples of scalar values:

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$25.45

750 meters

22.25 apples

.15 kittens (yuck!)

85.2 m/s

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Nearly every value you write in physics is going to be followed by a unit - the thing it is measured in.  The exceptions to this are coefficients - coefficient of friction, coefficient of restitution, etc.

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Vector quantities are scalar quantities plus an additional piece of information - direction.  Here are some examples of vector quantities:

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35 m/s, due north

15.2 m/s, up

-5.25 m

.85 m/s at an angle of 44 degrees with respect to the shoreline

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In physics, a negative sign is NEVER anything but a direction.  If right is positive then -5.25 m means 5.25 m to the left.  -13.4 m/s would mean a speed of 13.4 m/s to the left or down (up is positive).  Time is always scalar.  You can't have negative time without a tardis.

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Scalar Physics Quantities:                                                         Vector Physics Quantities:

speed                                                                                          velocity

distance                                                                                       displacement

time                                                                                              force

light intensity                                                                                acceleration

mass                                                                                            momentum

inertia                                                                                           torque

all forms of energy                                                                        weight

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Both scalar and vector quantities have a numerical value attached to them.  This is called the magnitude of the value.  For example, 131.8 m has a magnitude of 131.8 and a unit of meters.  The AP exam loves to ask you for the magnitude of an answer.  For example, "What is the magnitude of the velocity?"  This just means to give them the numerical value with the units.  You can literally read the question as, "What is the velocity?" and just leave off the direction.

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Think you've got it?  Go to this little quiz.  You can take it as many times as necessary.  Take a screen shot of your success.