10/11 Energy Practice

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10/11 Energy Practice

• Text Chapter 6 Energy
• HW 10/11 Ramp Launch due Wednesday 10/16
• Exam 2 Thursday, 10/17 5-7 Wit 116 6-8 Wit 114
  (only if needed)Please send email if other time
  neededAlso let me know if you are a 6-8 person

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The Kinetic Bucket...
KE PEg PEs E
KE 1/2mv2
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PE Gravity Bucket...
KE PEg PEs E
PEg mgh
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PE Spring Bucket...
KE PEg PEs E
PEs 1/2k?x2
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Work
cos ? means that forces perpendicular to the
motion do no work, cos 90 0.
Fother ?x cos ?
Other forces mean not gravity or springs
Also, Fother must be forces External to the
system. (Example was the tension force in Energy
and Friction homework)
Need to draw a FBD to find Work.
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Practice ProblemA block of mass M 10 kg
slides from rest down a frictionless ramp and
drops a distance h. After crossing a rough patch
the block compresses a spring with k 160 N/m an
amount ?x 0.5 m and comes to a momentary stop.
Find h.
A
v 0
?x 0.5 m
h?
?K 0.3
B
C
k 160 N/m
2 m