Calculate Hang Time of 2D Projectile Motion - TS

[ThetaPi]

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 \theta$ above the horizontal with an initial velocity of v_0, 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 (t_1), and the time it takes to hit the ground after attaining its maximum height (t_2), and then add up t_1+t_2. I think that it will be convenient to use the y-component of v_0.

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

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
TS

 

[dacruick]

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.

 

[ThetaPi]

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.

 

[dacruick]

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