# Physics

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The launching speed of a certain projectile is 6.4 times the speed it has at its maximum height. Calculate the elevation angle at launching.

• Physics -

The vertical component of velocity at max height is zero. The horizontal component remains Vh during flight, and that is the speed at max height. Let Voy be the initial vertical component of the launch speed.

(launch speed)^2 = Voy^2 + Vh^2
= (6.4 Vh)^2 = 40.96 Vh^2
Voy^2 = 39.96 Vh^2
Voy = 6.32 Vh
launch angle arctan(Voy/Vh) = arctan 6.32 = 81.0 degrees

• Physics -

How did you come up with 39.96 Vh^2?

• Physics -

I squared 6.4 and subracted 1. See the formula

Voy^2 + Vh^2 = 40.96 Vh^2

• Physics -

This is probably really obvious, but I'm still not undertanding why you have to subtract one.

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