02quiz_11

02quiz_11 - å vø h vø cos å vø sin å v √ å vø h...

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Unformatted text preview: å vø h vø cos å vø sin å v √ å vø h vø cos å vø sin å Physics 9A-C Quiz #2 Name: key 4/8/11 ID(last 4): A
rock
is
thrown
from
the
roof
of
a
building
with
a
velocity
 vø 
at
an
angle
 å

 from
the
horizontal.
 The
building
has
height
 h .

Ignore
air
resistance.

 a)

(8
points)
Find
the
speed
of
the
rock
just
before
it
hits
the
ground
and
show
that
the
speed
is
 independent
of
the
angle
å. Solution:


 a)

The
speed
is
the
magnitude
of
the
velocity

|
 v
√|
= 
 v x 2 + v y 2 

 (2
pts) so
we
need
to
find
the
components
of
the
velocity
just
before
is
hits
 the
ground.

 a x 
=
0

õ

v x 

=

vø cos
å

=
constant.

(2
pts)
 
Now
find
the
 y-component: We
could
use

 v y 
=

vø
 sin
å

-

 gt, 

but
then
we
would
need
to
eliminate
...
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This note was uploaded on 09/28/2011 for the course PHY 9A taught by Professor Svoboda during the Spring '08 term at UC Davis.

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