College Physics I: Day 6

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14 Νοε 2013 (πριν από 3 χρόνια και 7 μήνες)

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College Physics I: Day 6

Review & Kinematics Quiz

A bicyclist is riding at constant speed along a
straight path. The rider throws a ball straight up to a
height of a few meters above her head. Ignoring air
resistance, where will the ball
land?

A)
Ahead
of the
rider

B)
Behind
the
rider

C)
Directly
back in the hand that threw
it

D)
Depends
on the maximum height the ball
reaches

2

Concepts of Kinematics

Position (vector!)

Displacement (vector!)

Velocity (vector!)

Acceleration (vector!)

Understand the relationships among these

How does the direction of each relate to what is
happening to the object?

Be competent with vectors
and vector
mathematics


3

You are adding vectors of length 15 units and 35
units. Which of the following choices could
possibly be the magnitude of the
sum?

A)
0

B)
7

C)
18

D)
32

E)
56

4

A fighter jet must reach a speed of 165 mi/
hr

(73.8 m/s) to take off. On an aircraft carrier, the
available runway for takeoff is only
299
m long.
What is the minimum constant acceleration a plane
would need to take off on that
runway?

A)
1.11 m/s
2

B)
3.11 m/s
2

C)
5.11 m/s
2

D)
7.11 m/s
2

E)
9.11
m/s
2


5

Motion With Constant Acceleration

We can handle constant acceleration (or averaged)
in
one
dimension. Four
equations
apply
.

For two dimensions, each component must
be
treated
separately using the same tools.

For projectile motion:


Must split
into horizontal & vertical parts.


𝑎


=

9
.
8

𝑚
𝑠
2

and
𝑎


=



(
𝑣


is constant!)


Do not mix
horizontal & vertical quantities
!


You will usually need
to tackle both

6

Sample Problem

A boy throws a water balloon at and angle of 23
°

above horizontal and hits his friend who is 3.6
meters away. It
is in the air for 1.1 seconds.

How far did the balloon fall on its way?

What was the horizontal speed as it hit the friend
?


Other
Qs:

At what speed was the ball thrown?

At what angle did it hit the friend?


7

Quiz/Exam Four Question Types

True or False
: Choose T or F

Multiple choice
:

Choose one, no work needed


… but you should draw/calculate something

Short answer
:

Answer in (readable) sentences and/or diagrams.

Your explanation
counts more than your answer.

Problems
:

Traditional physics problems with occasional
conceptual
pieces.


8

Sample
Problem

Graph both
𝑥


vs
.

𝑡

and
𝑣


vs
.

𝑡
:

At
an amusement park
you wear a harness with a
bungee cord
attached.
The other end
is
secured to a
wall.
Then…

1.
You run steadily away
from the wall, reaching a
certain
location before
the cord becomes
taught.

2.
You continue
forward until you are stopped by
the bungee cord,
then go
flying backwards and
land on some pads
.

9

Coming up…

Right now → Quiz!

Wednesday (9/11) → 3.8


4.3


Warm
-
Up due Tuesday by 10:00 p.m.

Homework #4 (short!) due Saturday by 11:59 PM

10