Physics or math?

Find the maximum angle with the horizontal with which a projectile may be projected on earth so that its distance from the point of projection continuously increases.

Give your answer in degrees and up to 2 decimal places.

Assume we neglect variation of gravity.


The answer is 70.52.

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2 solutions

Let the position vector magnitude be r.then, r^2=x^2+y^2.differentiating the equation we get:(this will give expression for max distance) X/Y=-Vx/Vy solving this we will get a quadratic in t(time). for the distance to be increasing there should be no max distance or no real value of time. so in the quadritic equation(in t),putting b^2<4ac , we get sin(theta)<sqrt(8/9) theta<sin^-1(sqrt(8/9))~70.52.

Spandan Senapati
Aug 15, 2016

Fine.Good attempt.This problem s mathematical formulation is quite easy as you have already done .look for some physics out here.You will really enjoy after you get the trick.

What is the physics behind this?

Harsh Shrivastava - 4 years, 6 months ago

The critical case arises when the velocity and the displacement vector are orthogonal......you can use this to proceed further....or else refer to peter gnadigs"200 puzzling physics problems"

Spandan Senapati - 4 years, 6 months ago

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