Is it in motion?

• Look at the coke zero can sitting on my desk.

• You and your table needs to answer the following.

• 1. Is the can in motion relative to you and your classmates?

• 2. Is the can in motion at all?

• 3. Does the can’s motion depend on where I look at it from?

• 4. If the can is moving so fast through space why doesn’t it appear to be moving to us?

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Motion and Force

A. Motion

1. Motion is a change in position

2. Reference points are necessary

Frame of Reference

• A frame of Reference (reference point) is the object we use to compare distances, displacements, speeds, etc.

• To measure movement, some point must be considered as nonmoving.

• Earth is the most common frame of reference. Examples: buildings, trees, mountains, people standing, etc.

• It can sometimes be misleading, (think of the sun rising and setting) so be careful.

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Mr. Hansen likes to drag race his car.

• Drag racing has many reference points.

• The first is the starting line. (Christmas tree)

• Then there are reference points at various locations on the track. 60ft, 330ft, 1000ft, and at the end of the quarter mile 1320ft.

Reference points in drag racing

Sports use reference points

• Many different sports use reference points to determine motion.

• Football. (sidelines, yard marker, and end zone markers)

• Basketball. (half court, out of bounds, and three point shot.)

• Baseball. ( foul ball, bases, and home run)

• And many others.

A. Displacement vs. distance

1. Distance – how far

something moves (total)

2. Displacement – the

distance and direction

of an object’s change in

position from its starting point

B. Speed

1. The rate of change in position

2. Types of speed:

a. Instantaneous

b. Constant

c. Average

3. Speed = Distance / Time

C. Velocity

1. Speed in a defined direction

2. Velocity can change

even if speed is

constant as long

as direction

changes

D. Acceleration

1. The rate of change of velocity

2. a = (vf – vi) / t or a = v / t

3. Units are m/s/s

4. +a = speeding up; -a = slowing down

Example: constant speed & acceleration

Graphing to find Acceleration