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05_faq

Page history last edited by johnlittlephysics 10 years, 7 months ago

05 Work, Energy, Power FAQ


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Comments (4)

johnlittlephysics said

at 6:26 pm on Oct 10, 2013

302 Seok Mun: How do we calculate the energy lost due to friction force? For example, question 26 in
https://www.dropbox.com/s/hxlp6rf6tanpkbq/Photo%2010-10-13%206%2023%2009%20pm.jpg

johnlittlephysics said

at 6:38 pm on Oct 10, 2013

Energy lost due to friction is work done against friction = friction x distance moved along the slope.
For energy type of problems, general approach:
1. Identify the types of energy changes and/or work done (by a force or against friction)
2. Apply the Law of Conservation of Energy
In the question,
1. k.e. decreases, this transforms into gain in g.p.e. and some lost due to work done against friction f.
2. Loss in k.e. = gain in g.p.e + work done against f
1/2 m v ^2. = m g h + f x d
d is distance along slope, h/d = sin 60, so d = h/sin 60

Agalia said

at 8:30 pm on Mar 26, 2014

Hi Mr Ang. May I ask why is it that for the question (c), we subtract GPE from KE when in question 2 of AS5.1 (2013's), we add them together? Is it because the question is asking for work done and the other is not? Thanks.

johnlittlephysics said

at 8:06 pm on May 4, 2014

What is "question (c)"?

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