479 Horizontal Motion: The horizontal component of velocity ... - Wuala
479 Horizontal Motion: The horizontal component of velocity ... - Wuala
479 Horizontal Motion: The horizontal component of velocity ... - Wuala
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91962_05_R1_p0<strong>479</strong>-0512 6/5/09 3:53 PM Page 486<br />
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exist. No portion <strong>of</strong> this material may be reproduced, in any form or by any means, without permission in writing from the publisher.<br />
R1–10. A car travels at 80 ft>s when the brakes are<br />
suddenly applied, causing a constant deceleration <strong>of</strong><br />
10 ft>s 2 . Determine the time required to stop the car and<br />
the distance traveled before stopping.<br />
a : + b v = v 0 + a c t<br />
0 = 80 + (-10)t<br />
t = 8 s<br />
Ans.<br />
a : + b v 2 = v 2 0 + 2a c (s - s 0 )<br />
0 = (80) 2 + 2(-10)(s - 0)<br />
s = 320 ft<br />
Ans.<br />
R1–11. Determine the speed <strong>of</strong> block B if the end <strong>of</strong> the<br />
cable at C is pulled downward with a speed <strong>of</strong> 10 ft>s. What<br />
is the relative <strong>velocity</strong> <strong>of</strong> the block with respect to C?<br />
C<br />
10 ft/s<br />
3s B + s C = l<br />
3v B = -v C<br />
B<br />
3v B = -(10)<br />
v B = -3.33 ft>s = 3.33 ft>s c<br />
Ans.<br />
A +TB v B = v C + v B>C<br />
-3.33 = 10 + v B>C<br />
v B>C = -13.3 ft>s = 13.3 ft>s c<br />
Ans.<br />
486
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