Motion

• Change of position in respect to a reference point

Are you moving right now?

1 2

19%

81%1. Yes

2. No

• The whole galaxy rotates at 490,000 mph

• The earth ROTATES around its axis each day at 1,000 mph

Frames of Reference

Particular perspective from which an event in

the universe is observed

Example

• A woman on a moving truck throws a ball straight up in the air and the man next to her observes the flight path.

• Meanwhile, another man from the side of the road observes the same ball and is asked to describe the flight of the ball.

Speed

• Rate of change of position

s = d t• Three types: instantaneous, constant, average

speed

speeddistance

time

Instantaneous Speed

• Rate of motion at any given moment

• Ex/ speedometer, radar gun

This police officer finds “instantaneous speed!”

Constant Speed

• Speed that does not change or vary

• Ex/ setting cruise control on car

Average Speed

• Avg. speed = total distance traveled

total time

Speed Trap 1909

• Before the development of more advanced technology, police officers relied on the use of a simple stopwatch to time the passage of a car between two known and fixed positions.

• A 'speed trap' was set up by two policemen who began by carefully measuring a section of road and setting up two observations positions. One officer was placed at each end of the trap. As a car passed the first officer he made a signal (raised his hand etc.) and the second started his stopwatch. When the car passed the second fixed point, the other officer pressed the button to stop the watch - and had a measurement of the time taken to travel a known distance. The speed of the car could now be calculated (or found by referring to a book of tables). As cars travelled relatively slowly (perhaps 15-20 mph), the officer had time to step out and stop the car!

What type of speed is this showing?

1. Average speed

2. Constant speed

3. Instantaneous speed

4. Acceleration

4-Step Method for Solving Equations

• Define variables

• Choose Equation

• Rearrange equation (if necessary)

• Plug into equation and solve

Example

• A car leaves WHS and travels 10.3 km to Baker Park. It takes .15 hr to get there. What is the average speed?

Rearranging Equation

How FAR did a horse run if her pace was 7m/s for 30s? (assume constant speed)

HOW FAST IS FAST

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