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In the textbook Fundamentals of Physics by R. Shankar of Yale Open Courses, appears the following assertion pertaining to a car driving off a cliff, which seems correct:

This is exactly how long it would take to hit the ground had it simply toppled over the edge from rest. The horizontal velocity does not delay the crash one bit (unless you take into account the curvature of the earth).

However, at a later point in the book, Shankar makes the following claim about a bullet fired horizontally from a gun:

The bullet hits the ground at point 1, under the pull of gravity. If you fire another bullet at a greater velocity it will land a little further away, at point 2. While greater initial speed will extend the time of flight even on a flat earth, the flight is further enhanced by the earth curving under the bullet.

The claim that "While greater initial speed will extend the time of flight even on a flat earth..." seems to contradict the the initial claim.

Is this a blatant error on the part of the textbook?

Here is a link to the book if anybody is curious.

Buzz
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Trever Thompson
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2 Answers2

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I agree that the statement I made in the book is wrong: On a flat earth the time of flight is not affected by the initial horizontal velocity, only the horizontal distance is. I will post a correction in the errata in the website. Thank you for bringing this to my attention. R.Shankar Yale

R Shankar
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As @RatulThakur points out, this is pretty clearly an error. ToF is not affected at all by horizontal velocity on a flat Earth, unless you're considering the aerodynamics of the object (there's a reason why planes need to stay at a certain speed).

controlgroup
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