physics 1a, section 2
Post on 19-Jan-2016
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Second Quiz covers:
Frautschi chapters 4 - 8.4 (and 1 - 3) lectures/sections through yesterday (Oct. 20) homework #2-3 (and #1)
Quiz Problem 37
Quiz Problem 37
• Answer:
a) N = m2R, cos = g/(2R)
b) r = (R2 – g2/4)1/2
c) When <= (g/R)1/2, marble sits on bottom of bowl
Problem Solving Hints:
Normal Force and Friction suggested order:
1) draw gravity and other fixed external forces (direction and magnitude are unambiguous)
2) draw normal force (prevents interpenetration of objects)
3) draw friction force (perpendicular to normal force)
kinetic friction:
F = kNdirection opposite to relative velocity
static friction:
F ≤ sNdirection and magnitude to prevent relative acceleration
Quiz Problem 48:kineti
c frictio
n
Quiz Problem 48
• Answer:
a) m1a = T + m1g(sin – 1cos), m2a = -T + m2g(sin – 2cos)
b) a = g[sin – cos(m11+m22)/(m1+m2)], T = gcos(1-2)m1m2/(m1+m2)
c) 1 > 2
Quiz Problem 11: static
& kineti
c frictio
n
Quiz Problem 11
• Answer:
a) a = g(1scos - sin)
b) F = (m1+m2)g(2k + 1s)cos
Monday, October 25:
Quiz Problem 29 (non-inertial frames)
Quiz Problem 49 (springs)
Optional, but helpful, to try these in advance.
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