Finding the initial velocity of a projectile so that it hits a moving object

[bermy_son92]

Homework Statement

Object is 92m away from the projectile's launch position and is moving towards the launch position at 6m/s.
The projectile is launched at an angle of 72 degrees towards the moving object.
What must the projectile's velocity be if it is to hit the object moving towards it.
(Both the projectile and object start moving at the same time.)
acceleration = gravity = -9.8m/s

Homework Equations

distance=velocity/time
distance=velocity*time+0.5*acceleration*time^2
velocity2 - velocity1 = 2*acceleration*distance
velocity2 = velocity1 * acceleration * time

The Attempt at a Solution

I tried a few attempts however none of my ideas worked

 

[Phrak]

Why were the 5 or so subsequent messages posted here deleted?

 

[BlueFalcon]

Why were the 5 or so subsequent messages posted here deleted?

I uh... don't know. I'm new here. Don't know who could do that.

 

[Phrak]

I uh... don't know. I'm new here. Don't know who could do that.

I consider glitches, means, motive, and opportunity.

 

[ideasrule]

Until we get the posts back...

Homework Equations

distance=velocity/time
distance=velocity*time+0.5*acceleration*time^2
velocity2 - velocity1 = 2*acceleration*distance
velocity2 = velocity1 * acceleration * time

Note that your last two equations are wrong. The second-last one should be v2^2-v1^2=2ad, not v2-v1=2ad. The last one should be v2=v1+at, not v2=v1*a*t.

To solve this problem, write separate equations for the projectile's horizontal and vertical movements. In the y direction, the projectile leaves at speed=vsin72 and returns to its original height upon hitting the target. Suppose this takes time t. In the x direction, the projectile's relative speed to the target must be enough to cover 92 m in time t. Can you now write out two equations for the projectile's motion?