17. A jetliner leaves San Francisco for New York, 4600 km away. With a strong tailwind, its speed is 100 km/h. At the same time, a second jet leaves New York for San Francisco. Flying into the wind, it makes only 700 km/h. When and where do the two planes pass each other?
20. For the motion plotted in the figure (will be drawn in class on
a. the greatest velocity in the positive x direction
b. the greatest veocity in the negative x direction
c. any times when the object is instantaneously at rest
d. the average velocity over the interval shown.
46. A particle leaves its initial position xo at time t = 0, moving
in the positive x direction with speed vo, but undergoing acceleration
of magnitude a in the negative x direction. Find expressions for
a. the time when it returns to the position xo and
b. its pseed when it passes that point.
56. George, a physics student, leaves his dormitory at a speed of 1.2 m/s, heading for the physics building 95 m away. Just as he laeves his dorm, Amy, another physics student, leaves the physics building and heads toward George at a steady 1.6 m/s . George immediately spots her and begins accelerationg at 0.075 m/s2. Where and when do the two meet? Plot position-versus-time curves for both students on a single graph.
67. A falling object travels one-fourth of its total distance in the last second of its fall. From what height was it dropped?
69. A kingfisher is 30 m above a lake when it accidentally drops the
fish it is carrying. A seond kingfisher 5 m above the first dives toward
the falling fish. What initial speed should it have if it is to reach the
fish before the fish hits the water?
72. A conveyor belt moves horizontally at 80 cm/s, carrying empty shoe
boxes. Every 3 s, a pair of shoes is dropped from a chute 1.7 m above the
a. How far apart should the boxes be spaced?
b. At the instant a pair of shoes drops, where should a box be in relation to a point directly below the chute?
77. A frustrated student drops a book out of his dormitory window, releasing it from rest. After falling 2.3m, it passes the top of a 1.5 m high window on a lower floor. How long does it take to cross the window?
84. Consider an object traversing a distance l, part of the way at speed
v1 and the rest of the way at speed v2. Find expressions for the average
a. when the object moves at each of the two speeds for half the total time and
b. when it moves at each of the two speeds for half the distance.
91. A student is staring idly out her dormitory window when she sees
a water balloon fall past. If the balloon takes 0.22 s to cross the 130
cm high window, from what height above the top of the window was it dropped?