Physics

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Physics

• Physics The study of forces, motion and energy
• Motion Change in position over time compared to
  a reference point
• Reference Point object used to determine motion
  or position of an object ( can be non-moving
  or other moving objects)
• Speed Distance an object travels over a certain
  time period
• Formula speed distance
• time
• Common Units Miles mi/hr or mph ,
  kilometers km/hr, meters m/s
• hour hour
  second

Common Speeds Kangaroo 15 m/s Cheetah 27
m/s sound 343 m/s light 3 million m/s
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Speed

• 2 ways to describe speed
• Instantaneous speed Speed at any given moment
• Police officer clocks a car going 85 miles per
  hour, the officer has measured the cars
  instantaneous speed. A cars speedometer also
  measures instantaneous speed.
• Average Speed Total distance traveled divided by
  the total time. Most objects do not travel at a
  constant speed.
• Example Suppose a cheetah ran 270meters in 10
  seconds. What is his average speed?
• Average speed 270m/10s 27 m/s

Velocity Speed in a given direction
Examples 7 mph south 35 m/s west 85 km/hr
north
Formula Distance (with direction) Time
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Acceleration

• How quickly speed or velocity changes
• Occurs when an object speeds up, slows down
  (decelerates) or changes directions
• Formula final velocity Initial velocity
• time it took to change velocity
• Common units m/s/s, mi/hr/s, km/hr/s

Example 1 A car can travel from 0 mph to 60 mph
is 3 seconds, what is its acceleration?
Acceleration 60 mph 0mph 60mph
20mph 3 s
3 s s
Example 2 A car was traveling at 60 mph and
stopped in 3 seconds. What was the cars
acceleration?
Acceleration 0 mph 60mph - 60mph
-20mph 3 s
3 s s