KinematicsTime

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This set of slides may be updated this weekend. I have given you my current slides to get you started on the PreAssignment. Check back here frequently to see if updates have been made. I will post here a record of updates that have been made.

KinematicsTime

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So how do we define time for a physics problem?

Here are some rules of thumb to follow…

2. Each major physical change (event) should also be marked with its own time.a. We can also label these with an informative subscript or

superscript. (e.g. tDr. Mike’s sneeze or tcollision)b. Some events will actually occur at the same time like when Dr.

Mike sneezes that car collides with a tree. In this case we can give them the same name using either tDr. Mike’s sneeze or tcollision but not both.

Achoo!

Achoo!

KinematicsTime

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So how do we define time for a physics problem?

Here are some rules of thumb to follow…

3. We always assign variable names whether we have a value given in the problem or not.

4. The variable names mean the most when they contain both the object and the event. (Sometimes one or both of these are obvious and thus not written.)

5. It is best to create a table with variables and values to help organize our thoughts.

6. We leave unknown variables blank until we calculate them.

Variable Value

Dr. Mike leaves houset 6 : 20 am

Dr. Mike arrives at schoolt

KinematicsTime

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So how do we define time for a physics problem?

Here are some rules of thumb to follow…

3. For every time in our table it is a good idea to draw a picture.(The pictures do not have to be artistic, only informative.)

Variable Value

Dr. Mike leaves houset 6 : 20 am

Dr. Mike arrives at schoolt

Dr. Mike leave house Dr. Mike arrivesAt school

NMSU

KinematicsTime

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Here are some examples.

Example #1

Given the problem…

Dr. Mike leaves for school in his Toyota Corolla at 10:00am. Bailey D. Wonderdog follows him exactly 50 minutes later. Dr. Mike (being a safe driver) drives 5 mph below the speed limit (65 mph to be exact); whereas, Bailey (being a superhero) has the need for speed and drives at 70 mph. How long will it take for Bailey to catch up with Dr. Mike?

What are the times we must take into account?

Your answers

KinematicsTime

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Here are some examples.

Example #2

Given the problem…

A ball is dropped from a cliff. The cliff’s height is 20 m. The ball falls under the influence of gravity only (free-fall). When it reaches the bottom, it bounces three times before rolling to a stop. How fast is it going just before it reaches the ground after falling from the cliff?

What are the times we must take into account?

Your answers