- (II) A child, who is 45 m from the bank of a river, is being carried helplessly downstream by the river's swift current of 1.0 m/s. As the child passes a lifeguard on the river's bank, the lifeguard starts swimming in a straight line (Fig. 3–46) until she reaches the child at a point downstream. If the lifeguard can swim at a speed of 2.0 m/s relative to the water, how long does it take her to reach the child? How far downstream does the lifeguard intercept the child? 1.0 m/s 2.0 m/s - 45 m FIGURE 3-46 Problem 49.

- (II) A child, who is 45 m from the bank of a river, is being carried helplessly downstream by the river's swift current of 1.0 m/s. As the child passes a lifeguard on the river's bank, the lifeguard starts swimming in a straight line (Fig. 3–46) until she reaches the child at a point downstream. If the lifeguard can swim at a speed of 2.0 m/s relative to the water, how long does it take her to reach the child? How far downstream does the lifeguard intercept the child? 1.0 m/s 2.0 m/s - 45 m FIGURE 3-46 Problem 49.

College Physics

11th Edition

ISBN:9781305952300

Author:Raymond A. Serway, Chris Vuille

Publisher:Raymond A. Serway, Chris Vuille

Chapter1: Units, Trigonometry. And Vectors

Section: Chapter Questions

Problem 1CQ: Estimate the order of magnitude of the length, in meters, of each of the following; (a) a mouse, (b)...

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(II) A passenger on a boat moving at 1.70 m/s on a still lake walks up a flight of stairs at a speed of 0.60 m/s, Fig. 3–43. The stairs are angled at 45° pointing in the direction of motion as shown. What is the velocity of the passenger rel- ative to the water? 0.60 m/s y 45° V = 1.70 m/s FIGURE 3-43 Problem 42.
(III) Sketch the v vs. t graph for the object whose displacement as a function of time is given by Fig. 2–44
(II) A boat, whose speed in still water is 2.50 m/s, must cross a 285-m-wide river and arrive at a point 118 m upstream from where it starts (Fig. 3–45). To do so, the pilot must head the boat at a 45.0° upstream angle. What is the speed of the river's current? +118 m→ Finish River `current 285 m 45.0° FIGURE 3-45 Start Problem 48. Path of boat
(II) Extreme-sports enthusiasts have been known to jump off the top of El Capitan, a sheer granite cliff of height 910 m in Yosemite National Park. Assume a jumper runs horizontally off the top of El Capitan with speed 4.0 m/s and enjoys a free fall until she is 150 m above the valley floor, at which time she opens her parachute (Fig. 3–37). (a) How long is the jumper in free fall? Ignore air resis- tance. (b) It is important to be as far away from the cliff as possible before opening the parachute. How far from the cliff is this jumper when she opens her chute? 4.0 m/s 910 m 150 m FIGURE 3-37 Problem 26.
(II) A person in the passenger basket of a hot-air balloon throws a ball horizontally outward from the basket with speed 10.0 m/s (Fig. 3–44). What initial velocity (magni- tude and direction) does the ball have relative to a person standing on the ground (a) if the hot-air balloon is rising at 3.0 m/s relative to the ground during this throw, (b) if the hot-air balloon is descending at 3.0 m/s relative to the ground? 10.0 m/s FIGURE 3-44 Problem 43.
(II) A ball player catches a ball 3.4 s after throwing it vertically upward. With what speed did he throw it, and what height did it reach?
(II) Two planes approach each other head-on. Each has a speed of 780km/h and they spot each other when they are initially 10.0 km apart. How much time do the pilots have to take evasive action?
(II) A horse trots away from its trainer in a straight line, moving 38 m away in 9.0 s. It then turns abruptly and gallops halfway back in 1.8 s. Calculate (a) its average speed and (b) its average velocity for the entire trip, using“away from the trainer” as the positive direction
(III) Two cars approach a street corner at right angles to each other (Fig. 3–47). Car 1 travels at a speed relative to Earth vIE = 35 km/h, and car 2 at v2E = 55 km/h. What is the relative 2 velocity of car 1 as seen by car 2? What is the velocity of car 2 relative to car 1? 2E 1E FIGURE 3-47 Problem 51.
(II) A rescue plane wants to drop supplies to isolated moun- tain climbers on a rocky ridge 235 m below. If the plane is traveling horizontally with a speed of 250 km/h (69.4 m/s), how far in advance of the recipients (horizontal distance) must the goods be dropped (Fig. 3–38)? Vx0 "Dropped" (vyo=0) 235 m FIGURE 3-38 Problem 31.
(III) A diver leaves the end of a 4.0-m-high diving board and strikes the water 1.3 s later, 3.0 m beyond the end of the board. Considering the diver as a particle, determine: (a) her initial velocity, vo; (b) the maximum height reached; and (c) the velocity vf with which she enters the water.
(II) The best rebounders in basketball have a vertical leap (that is, the vertical movement of a fixed point on their body) of about 120 cm. (a) What is their initial “launch” speed off the ground? (b) How long are they in the air?