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What is hang time?

by ThetaPi
Tags: time
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Mar19-10, 07:53 AM
P: 9
Could someone kindly explain to me what hang time is, in the context of 2D projectile motion? Enlighten me on the equations of motion that might be applicable to such a problem.

In other words, given a projectile launched at [tex]\theta$[/tex] above the horizontal with an initial velocity of [tex]v_0[/tex], how do we calculate the hang time?

Thoughts. We need to calculate the time it takes for the projectile to reach the maximum height of the trajectory ([tex]t_1[/tex]), and the time it takes to hit the ground after attaining its maximum height ([tex]t_2[/tex]), and then add up [tex]t_1+t_2[/tex]. I think that it will be convenient to use the y-component of [tex]v_0[/tex].

The maximum height of the trajectory is [tex]|1/2gt_2^2|[/tex]. We can use this in the equation [tex]s_y=v_{0y}t_1-1/2gt_1^2[/tex] to find [tex]t_1[/tex].

I am rather confused...some posts I saw while browsing the forums said that the initial velocity does not affect the "hang time".

Thank you
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Mar19-10, 08:16 AM
P: 1,084
velocity in the x-direction doesn't have an affect on hang time. hang time to me is simply the time that the projectile is in the air.
Mar19-10, 08:18 AM
P: 9
I know that, but how do we calculate that numerically?

I presume that hang time is dependent on the y-component of the initial velocity?

Thanks again.

Mar19-10, 08:25 AM
P: 1,084
What is hang time?

right. you've written the equation that is going to give you the answer. If it is a projectile starting and stopping at the same y value, you know that maximum height has to be at half the total time its in the air. try working through it you seem to understand the concept

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