mt2sol_11a

mt2sol_11a - Phy 9A-C Midterm 2 Solutions Page 1 of 2...

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Unformatted text preview: Phy 9A-C, Midterm 2 Solutions, Page 1 of 2 5/20/11 Yellow F T F N mg f F N mg f Phyiscs 9A-C Midterm 2 Solutions Cole Yellow [1]

a)
Í
F√

=

0

b)
never,

c)
both,

d)
position,

e)
equal
to,

f)
spin
faster,


g)
 K m 
>
K M ,


 h)
none,


i)
0,


j)

momentum. [2]

a)
(10
pts) 
 Use
the
work
energy
theorem

 W T 
=
ÎK.


 
 W F T = F T Δ x = 500
N ( ) 5
m ( ) = 2500
J While
 F N 
 does
no
work
it
is
needed
for
the
 friction
force:

Í F y 
=
F N 
-
mg 
cos
36.9°

=
0
õ
 
 F N = mg cos36.9 ° = 4 5 mg 

õ
 
 W f = − μ k F N Δ x = − μ k 4 5 mg Δ x 
õ
 
 W f = − 0.35 ( ) 4 5 30
kg ( ) 9.8
m/s 2 ( ) 5
m ( ) = − 411.6
J .

 The
only
other
force
doing
work
is
gravity:

 
 W g = − mg ′ h = − 30
kg ( ) 9.8
m/s 2 ( ) 3
m ( ) = − 882.0
J882....
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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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mt2sol_11a - Phy 9A-C Midterm 2 Solutions Page 1 of 2...

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