Two boats are headed across a calm bay in the same direction, West. One is a sai

Question

Two boats are headed across a calm bay in the same direction, West. One is a sailboat, and a sudden change in the wind causes it to experience an acceleration to the East. The other is a motorboat, which is unaffected by the wind and is still accelerating to the West. After a small period of time, delta t, both have the same velocity. Draw a graphical representation of their velocities as a function of time. Which, if either, boat is speeding up? Why do you say this? Which boat is initially going faster? Justify your answer. In the time delta t, which one went farther? Justify your answer. A physics student, frustrated with his homework, decides to be done with physics by dropping his book from a window 5 m up from the ground into a hole of unknown depth. He thought that in lieu of homework he should make one last real-world physics calculation. So, he listens for the Thump, then records the time of flight. The thump came 3 seconds after the release. He wonders how deep the hole is so he pulls out his pencil and paper and makes a quick calculation. He uses the approximation of zero air resistance. How deep is the hole? How fast was the book moving when it hit?

Explanation / Answer

3.

suppose depth of hole is h then ,

total vertical displacement, y = - 5 - h

initial velocity, v0 = 0

Applying y = v0 t + a t^2 / 2

- 5 - h = 0 - (9.8 x 3^2 / 2 )

- 5 - h = - 44.1

h = 39.1 m

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