# Lecture 4 Wednesday Sept 3x

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14 Νοε 2013 (πριν από 4 χρόνια και 6 μήνες)

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Physics 31

Lecture 4

Clicker Test

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The kinematics of motion in
one dimension

Problem
-
solving strategies

Free fall

Chapter 2

Motion in One Dimension

Topics:

Sample question:

Horses can run much
much

faster than humans, but if the length
of the course is right, a human can beat a horse in a race. When,
and why, can a man outrun a horse?

Slide 2
-
1

From this class:

In Chapter 1 you began studying motion in one dimension. We
continue the development of the concepts in this chapter.

In Chapter 1 you saw how to represent motion using a motion
diagram. In this chapter we will look at other ways to represent
motion.

From previous classes:

We will use graphical representations of motion extensively in
this chapter. You should have learned how to draw, interpret,
and work with graphs in previous courses.

Slide 2
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Looking Back: What You Already Know

Representations

Slide 2
-
9

Motion diagram (student walking to school)

Table of data

Graph

Solving Problems

Slide 2
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Slide 2
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Solving Problems (continued)

Interpreting Graphs

Slide 2
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Here is a motion diagram of a car moving along a straight stretch

Which of the following velocity
-
versus
-
time graphs matches this
motion diagram?

Checking Understanding

A.

Slide 2
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B.

C.

D.

Here is a motion diagram of a car moving along a straight stretch

Which of the following velocity
-
versus
-
time graphs matches this
motion diagram?

Slide 2
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C.

Checking Understanding

Slide 2
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A graph of position versus time for a
basketball player moving down the
court appears like so:

Which of the following velocity graphs matches the above
position graph?

A.

B.

C.

D.

Slide 2
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16

A graph of position versus time for a
basketball player moving down the
court appears like so:

Which of the following velocity graphs matches the above
position graph?

C.

A graph of velocity versus time for a
hockey puck shot into a goal appears
like so:

Which of the following position graphs matches the above
velocity graph?

Checking Understanding

A.

B.

C.

D.

Slide 2
-
17

A graph of velocity versus time for a
hockey puck shot into a goal appears
like so:

Which of the following position graphs matches the above
velocity graph?

D.

Slide 2
-
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Examples

A soccer player is 15 m from her opponent’s goal. She kicks the
ball hard; after 0.50 s, it flies past a defender who stands 5 m
away, and continues toward the goal. How much time does the
goalie have to move into position to block the kick from the
moment the ball leaves the kicker’s foot?

Cleveland and Chicago are 340 miles apart by train. Train A
leaves Cleveland going west to Chicago at 1:00 PM, traveling at
60 mph. Train B leaves Chicago going east to Cleveland at 2:00
PM, going 45 mph. At what time do the two trains meet? How far
are they from Chicago at this time?

Slide 2
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The slope at a point on a position
-
versus
-
time graph of an

object is

the object’s speed at th..
the object’s average velo...
. the object’s instantane...
the object’s acceleration ..
the distance traveled by...
0%
0%
0%
0%
0%
A.
the object’s speed at
that point.

B.
the object’s average
velocity at that point

C.
. the object’s
instantaneous
velocity at that point.

D.
the object’s
acceleration at that
point.

E.
the distance traveled
by the object to that
point.

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The area under a velocity
-
versus
-
time graph of an object is

the object’s speed at th..
the object’s acceleration ..
the distance traveled by...
the displacement of the...
None of the above
0%
0%
0%
0%
0%
A.
the object’s speed at
that point.

B.
the object’s
acceleration at that
point.

C.
the distance traveled
by the object.

D.
the displacement of
the object.

E.
None of the above

Homework for today

Problems:
1:
28, 30, 32, 35, 43, 47, 51, 56

Homework for Friday