50 40 30- 20 10- -10 10 20 30 10 Danny is a lifeguard and spots a drowning child 30 meters along the shore and 50 meters from the shore to the child. Danny runs along the shore for a while and then jumps into the water and swims from there directly to the child. Danny can run at a rate of 5 meters per second and swim at a rate of 0.9 meters per second. How far along the shore should Danny run before jumping into the water in order to save the child? Round your answer to three decimal places.

50 40 30- 20 10- -10 10 20 30 10 Danny is a lifeguard and spots a drowning child 30 meters along the shore and 50 meters from the shore to the child. Danny runs along the shore for a while and then jumps into the water and swims from there directly to the child. Danny can run at a rate of 5 meters per second and swim at a rate of 0.9 meters per second. How far along the shore should Danny run before jumping into the water in order to save the child? Round your answer to three decimal places.

Principles of Physics: A Calculus-Based Text

5th Edition

ISBN:9781133104261

Author:Raymond A. Serway, John W. Jewett

Publisher:Raymond A. Serway, John W. Jewett

Chapter13: Mechanical Waves

Section: Chapter Questions

Problem 1CQ

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A spacecraft zooms past the Earth with a constant velocity. An observer on the Earth measures that an undamaged clock on the spacecraft is ticking at one-third the rate of an identical clock on the Earth. What does an observer on the spacecraft measure about the Earth-based clock's ticking rate? (a) It runs more than three times faster than his own clock. (b) It runs three times faster than his own. (c) It runs at the same rate as his own. (d) It runs at one-third the rate of his own. (e) It runs at less than one-third the rate of his own.
Suppose an astronaut is moving relative to the Earth at a significant fraction of the speed of light. (a) Does he observe the rate of his clocks to have slowed? (b) What change in the rate of Earth-bound clocks does he see? (c) Does his ship seem to him to shorten? (d) What about the distance between stars that lie on lines parallel to his motion? (e) Do he and an Earth-bound observer agree on his velocity relative to the Earth?
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An observer in a coasting spacecraft moves toward a mirror at speed v relative to the reference frame labeled by S in Figure P26.46. The mirror is stationary with respect to S. A light pulse emitted by the spacecraft travels toward the mirror and is reflected back to the spacecraft. The spacecraft is a distance d from the mirror (as measured by observers in S) at the moment the light pulse leaves the spacecraft. What is the total travel time of the pulse as measured by observers in (a) the S frame and (b) the spacecraft? Figure P26.46
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