Physics Unit One

1
Physics Unit One

• Motion

2
Motion

• Any change in the position of an object.
• Can be completely described with speed and
  direction.

3
Distance vs. Displacement

• How far the object has traveled
• Add up all lengths of all the segments of travel
• Just a length (mm, cm, km)

• How far the object is from the starting point
• ?x xf xi
• Length and direction (/- mm, cm North, km away
  from Mr. Burr

4
Speed vs. Velocity

• The distance an object travels per unit of time.
• s d / t
• Units - any distance over any time.
• Ex. m/s, km/hr, cm/s, etc

• Speed PLUS direction.
• A vector quantity
• (magnitude direction)
• v d / t, direction
• Units any distance over any time, plus,
  direction.
• Ex. 6.5 cm/s, due north

5
5-Step Method for Solving Problems

• A cat can run 5.0 meters in 3.25 seconds. What
  is the cats average speed?
• d 5.0 m
• t 3.25 s
• s d / t
• s 5.0m / 3.25s
• s 1.54 m/s

6
Velocity Sample Problem

• A tennis ball flies off the end of a racket and
  travels 10.0 meters in 0.95s. What is the
  velocity of the tennis ball?
• d 10.0 m
• t 0.95s
• v d / t
• v 10.0m / 0.95s
• v 10.53 m/s, across the net

7
Mini Speed Lab
8
Experimental Error

• Unavoidable errors caused by difficulties or
  uncertainties in the procedure.
• DO NOT INCLUDE AVOIDABLE HUMAN ERRORS. We did it
  wrong. We measured wrong.
• DO NOT BLAME YOUR LAB PARTNER
• My lab partner messed it up. My lab partner
  pushed the cart instead of letting it fall.
• DO NOT BLAME THE EQUIPMENT. Our spring
  scale was not zeroed properly. We read the
  balance wrong. Our cart had a wobbling wheel.

9
Experimental Error

• Look at the equation. What was measured? What
  possible errors exist in these measurements?
• Were any steps of the procedure especially
  difficult to complete? What errors could this
  cause to your data?
• In Physics, if you have lots of error use the
  F word FRICTION!