# Fisica

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• Publicado : 16 de marzo de 2011

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1 In Fig. 5-21, forces F1 and F2 are applied to a lunchbox as it slides at constant velocity over a frictionless floor. We are to decrease angle ϴ without changing the magnitude of F1.
For constantvelocity, should we increase, decrease, or maintain the magnitude of F2?
3 Figure 5-22 shows overhead views of four situations in which forces act on a block that lies on a frictionless floor. If theforce magnitudes are chosen properly, in which situations is it possible that the book is (a) stationary and (b) moving with constant velocity?
5. Figure 5-24 gives the free body diagram for foursituations in which an object is pulled by several forces across a frictionless floor, as seen from overhead. In which situations does the object’s acceleration a have (a) an x component and (b) a ycomponent? (c) In each situation, five the direction of a by naming either a quadrant or a direction along an axis. (This can be done with a few mental calculations.)
6. Figure 5-25 gives three graphsof velocity component vy(t). The graphs are not to scale. Which vx(t) graph and which vy(t) graph best correspond to cach four situations in Questions 5 and Fig 5-24?
7. Figure 5-26 shows a train offour blocks being pulled across a frictionless floor by force F. What total mass in accelerated to the right by (a) force F, (b) cord 3, and (c) cord 1? (d) Rank the blocks according to theiraccelerations, greatest first. (e) Rank the cords according to their tension, greatest firs. (Warm-up for problems 50 and 51)
8. Figure 5-27 shows the same breadbox in four situations where horizontal forcesare applied. Rank the situations according to the magnitude of the box’s acceleration, greatest first.
9. A vertical force F is applied to a block of mass m that lies on a floor. What happens to themagnitude of the normal force FN on the block from the floor as magnitude F is increased from zero if force F is (a) downward and (b) up-ward?
10. Figure 5-28 shows four choices for the direction...