Concept explainers
A fisherman sets out upstream on a river. His small boat, powered by an outboard motor, travels at a constant speed v in still water. The water (Urn’s at a lower constant speed vw. The fisherman has traveled upstream for 2.00 km when his ice chest falls out of the boat. He notices that the chest is missing only after he has gone upstream for another 15.0 min. At that point, he turns around and heads back downstream, all the time traveling at the same speed relative to the water. He catches up with the floating ice chest just as he returns to his starting point. How last is the river flowing? Solve this problem in two ways. (a) First, use the Earth as a reference frame. With respect to the Earth, the boat travels upstream at speed v − vw, and downstream at v + vw. (b) A second much simpler and more elegant solution is obtained by using the water as the reference frame. This approach has important applications in many more complicated problems; examples are calculating the motion of rockets and satellites and analyzing the scattering of subatomic particles from massive targets.
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Chapter 4 Solutions
Physics for Scientists and Engineers
- At t = 0, a particle moving in the xy plane with constant acceleration has a velocity of vi=(3.00i2.00j)m/s and is at the origin. At t = 3.00 s, the particles velocity is vf=(9.00i+7.00j)m/s. Find (a) the acceleration of the particle and (b) its coordinates at any time t.arrow_forwardDoes a car moving around a circular track with constant speed have (a) zero acceleration, (b) an acceleration in the direction of its velocity, (c) an acceleration directed away from the center of its path, (d) an acceleration directed toward the center of its path, or (e) an acceleration with a direction that cannot be determined from the given information?arrow_forwardA plane that is capable of travelling at 140 m/s wishes to travel due north from City A to City B, 500 km away, but encounters a constant crosswind that blows 25 m/s due west. What must the plane’s heading be in order to reach its destination? Suppose the pilot has no navigational expertise and decides to aim straight for City B. How far west of City B will the plane end up?arrow_forward
- The turd is launched at a speed of 49 m/s at an angle 54 degrees above the horizontal. At exactly what time after the launch should the ground be covered in a portal to intercept the turd before it hits the ground?arrow_forwardAt one instant a bicyclist is 40.0 m due east of a park’s flagpole, going due south with a speed of 10.0 m/s.Then 30.0 s later, the cyclist is 40.0 m due north of the flagpole, going due east with a speed of 10.0 m/s. For the cyclist in this 30.0 s interval, what are the (a) magnitude and (b) direction of the displacement, the (c) magnitude and (d) direction of the average velocity, and the (e) magnitude and (f) direction of the average acceleration?arrow_forwardA student drives 10 km to the north and then 20 km 30 degrees S of E. By using the component method, what are the magnitude and direction of his displacement from the starting point?arrow_forward
- A stone is thrown horizontally from the highest point of a 95 m building and lands 115 m from the base of the building. Ignore air resistance, and use a coordinate system whose origin is at the highest point of the building, with positive y upwards and positive x in the direction of the throw. How long is the stone in the air in seconds? What must have been the initial horizontal component of the velocity, in meters per second? What is the vertical component of the velocity just before the stone hits the ground, in meters per second? What is the magnitude of the velocity of the stone just before it hits the ground, in meters per second?arrow_forwardAn inflatable life raft is released from an air plane at 500 m altitude, in level flight, with an air speed of 20 m/s in the horizontal direction. How long before the raft strikes the water? How far from the release point does the raft strike the water?arrow_forwardAt one instant, a bicyclist is 50 m due east of a park's flagpole, going due south with a speed of 18 m/s. Then, 13 s later, the cyclist is 45 m due north of the flagpole, going due east with a speed of 13 m/s. For the cyclist in this 13 s interval, what is the displacement (m) and direction north of west, average velocity (m/s) and direction north of west and the average acceleration and direction north of east?arrow_forward
- A canon fires its shell out at a speed of 161.4m/s and at an angle of 36 degrees above horizontal. How long will it take for the sheel to come back down, assuming a level ground?arrow_forwardAn inflatable life raft is released from an airplane at 300 m altitude, in level flight, with an air speed of 100 m/s in the horizontal direction. At what horizontal distance from the release point does the raft strike the water?arrow_forwardA spacecraft is traveling through space parallel to the x direction with an initial velocity of magnitude v0 = 3070 m/s. At t = 0 the pilot turns on the engines, producing an acceleration of magnitude a = 169 m/s2 along the y direction. Find the speed and the angle that the velocity makes with the x direction at (a) t = 20 s speed? angle in degrees? (b) 49 s. speed? angle in degrees?arrow_forward
- Principles of Physics: A Calculus-Based TextPhysicsISBN:9781133104261Author:Raymond A. Serway, John W. JewettPublisher:Cengage Learning