Physics 1A, Section 6

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Physics 1A, Section 6

• October 6, 2008

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Section Business

• Section 6 office hour
• Caltech/Downs 101
• Tuesdays 400 - 530 PM
• See other choices on course web site
• http//www.its.caltech.edu/tmu/ph1a
• Section web site
• http//www.submm.caltech.edu/cdd/PHYS1A_2008

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Week 1 Reading/Lecture Review

• T.M.U. chapters 1-2 lectures
• units dimensions
• dimensional analysis (estimation)
• law(s) of falling bodies
• constant acceleration (compare eq. 2.14-2.16)
• s s0 v0t ½ at2
• v v0 at
• distance, velocity, acceleration (general case)
• v ds/dt
• a dv/dt

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A modern look athistorical laws of falling bodies

• Oresme (14th century)
• v ? t
• s ? t2
• (both correct)

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A modern look athistorical laws of falling bodies

• Galileo (17th century)

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A modern look athistorical laws of falling bodies

• Galileo (17th century)

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A modern look athistorical laws of falling bodies

• Galileo (17th century)
• s ? t2 (correct)

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A modern look athistorical laws of falling bodies

• da Vinci (15th century)

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A modern look athistorical laws of falling bodies

• da Vinci (15th century)

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A modern look athistorical laws of falling bodies

• da Vinci (15th century)
• s ? (t)(t 1)/2 t2/2 t/2

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A modern look athistorical laws of falling bodies

• da Vinci (15th century)
• s ? (t)(t 1)/2 t2/2 t/2
• v ds/dt ? t 1/2 (moving at the start)

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A modern look athistorical laws of falling bodies

• Albert of Saxony (14th century)
• v ? s

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A modern look athistorical laws of falling bodies

• Albert of Saxony (14th century)
• v ? s
• ds/dt ks

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A modern look athistorical laws of falling bodies

• Albert of Saxony (14th century)
• v ? s
• ds/dt ks
• s Cekt

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A modern look athistorical laws of falling bodies

• Albert of Saxony (14th century)
• v ? s
• ds/dt ks
• s Cekt
• v Ckekt

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A modern look athistorical laws of falling bodies

• Albert of Saxony (14th century)
• v ? s
• ds/dt ks
• s Cekt
• v Ckekt
• Takes an infinite time to start from
  infinitesimal velocity!

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Quiz Problem 35
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Quiz Problem 35

• Answer
• a) a(t) jt a0
• v(t) jt2/2 a0t v0
• x(t) jt3/6 a0t2/2 v0t x0
• b) (see graph)
• c) A was ahead at t 0.5 s.
• d) J will win.

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Quiz Problem 46
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Quiz Problem 46

• Answer
• a) D VsT
• sqrtW2 (X-VrT)2
• b) tan q (X-VrT)/W
• c) Vs gt Vr
• d) (Vs2-Vr2)T2 2XVrT (W2X2) 0
• Use quadratic formula.
• e) T W/sqrtVs2-Vr2
• f) T W/Vs
• X WVr/Vs

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Thursday, October 9

• T.M.U., Problem 3-7
• Quiz Problem 19
• Optional, but helpful, to look at these in
  advance.