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0593_C05_fm Page 161 Monday, May 6, 2002 2:15 PM
Planar Motion of Rigid Bodies — Methods of Analysis 161
and
Q
V =−50 n + 120 n cen sec
x y
where n and n are horizontal and vertical unit vectors as in Figure P5.7.2. Determine
x
y
(a) the coordinates of the instant center C of B, (b) the angular velocity ω of B, and (c) the
velocity of point A of B (in terms of n and n ), whose coordinates are (30, 10).
x
y
Y
n y Q(25,13)
P(13,8) A(10,30)
B
FIGURE P5.7.2 O
A body B in planar motion with X
known velocities of two points. n x
Section 5.8 Instant Center of Zero Acceleration
P5.8.1: A 2-ft-radius circular disc rolls to the right, with its center O having a speed of 3.5
ft/sec, as in Figure P5.8.1. The disc, however, is decelerating so that O has an acceleration
to the left of 1.5 ft/sec . Determine the X–Y coordinates of the center at zero acceleration.
2
Y
2 ft
O
a = 1.5 ft/sec v = 3.5 ft/sec
2
O O
FIGURE P5.8.1
A rolling but decelerating circular C X
disc.