Easy question

1
Easy question

• Are you moving?
• That might SEEM to be an easy question
• Shall we try to answer it?
• Are you moving?
• Yes?
• No?
• Hard to answer.why???

2
There are stupid questions!!

• Are you moving?
• One cannot possibly answer that question without
  asking another question first
• Let me give you a hint
• Are you tall?
• Are you smart?
• Do you run fast?
• Are you rich?

3
And the answer is????

• Why was it difficult to answer those
  questions.???
• What was needed??
• A FRAME OF REFERENCE!!!

4
A Frame of Reference

• A frame of reference is some standard we use to
  make a comparison.
• NO judgment can be made without some frame of
  reference.
• I got a 2450 on the PMTS test. Is that good?
• You need a frame of reference.
• I have a PTTP level in my blood of 44. Is that
  OK??

5
SO???? Are you moving?

• Yes, I am moving compared to..
• No, I am not moving compared to
• Are you tall?
• Yes, I am tall relative to.
• No, I am not tall relative to.
• Everyone in the room point to the left please.
• You can see from this that even left and right
  vary considerably. SOin this class room we will
  NEVER use left, right, up or down as directions.
  We will use compass points . We will talk about
  North, South, East or West. That will be our F OF
  R.

6
Qualitative motion

• That car is going too fast.
• That turtle moves so slowly.
• Lava can flow faster than water.
• He is changing his speed.

7
What is motion?

• Motion is a change of position relative to some
  frame of reference.
• Motion can be quantitative or qualitative.
• Quantitative is a description of anything using
  numbers, measurements, MATH. We say that this is
  an objective description. This is MUCH favored in
  all sciences!!
• Qualitative is a description of anything using
  adjectives. We say this is more subjective,
  sometimes no more than an opinion. It is the goal
  of all sciences to REMOVE opinion from
  conclusions!

8
Quantitative motion

• Motion is a change of position relative to some
  frame of reference.
• Motion can be described in terms of distance or
  displacement as a function of time. It can be
  MEASURED. That is quantifying our descriptionwe
  are happy.
• From distance and time we can calculate speed and
  go on to measure acceleration.
• So we might say the wagon is going 40.

9
40? 40 WHAT??

• The other frame of reference we use in science is
  the unit for all numbers. It is the frame of
  reference for the digits which by themselves have
  very little meaning!
• Thus we can describe motion as a change of
  position relative to some F OF R.

10
Displacement

• Joe Schmoe walks 10 blocks North, turns East and
  walks 10 blocks then turns and walks 10 blocks
  South.
• What is Joes distance?
• What is Joes displacement?
• You need to answer 30 blocks is the distance but
  he is 10 blocks EAST as his displacement.

11
Scalar vs vector

• Notice we said he walked 30 blocksthat was his
  distance it was simply the total length of the
  path he took. This is a scalar.
• BUT his displacement had a direction10 blocks
  East of where he started. This is a vector.
• A scalar is any quantity where direction is not a
  factor
• A vector is any measurement that must include a
  direction because it IS a factor.
• Mass, speed, distance are examples of scalars.
• Weight, forces, displacement are examples of
  vectors.
• We will speak more about scalars and vectors as
  we move on.

12
Distance vs Displacement

• To move means to cover some distance or
  accomplish some displacement.
• Distance is the total length of the path
  takenyou walked 40 feet or drove 40 kilometers
  or measured the distance the ball was kicked to
  be 40 yards.
• Displacement on the other hand is slightly
  different in concept. Displacement is how far you
  are from where you started. You may walk a total
  distance of 30 blocks but end up only 10 blocks
  from where you started.
• Map out that example. How could you walk 30
  blocks but have a displacement of only 10 blocks
  from your start position.

13
QUIZ

• On the quiz the next time we meet look for these
  questions
• 1. Distinguish between
• Moving and not moving
• Distance vs displacement
• Stupid questions vs smart questions
• 2. What is a frame of reference and give two
  examples where a frame of reference is essential.