How should a hunter aim to hit a target? Kinematics problem

[slayerdeus]

A hunter aims directly at a target (on the same level) 120 m away.
(a) If the bullet leaves the gun at a speed of 300 m/s, by how much will it miss the target?
(b) At what angle should the gun be aimed so the target will be hit?

Im havin a little trouble here. I think you are supposed to find how far it goes horizontally. But how can you find this, when you don't know how high they are?

 

[Doc Al]

Im havin a little trouble here. I think you are supposed to find how far it goes horizontally. But how can you find this, when you don't know how high they are?

You know how far it travels horizontally. You need to figure out how far it falls (vertically). Figure out the time takes for the bullet to travel that horizontal distance. Then figure out how far it falls in that time.

 

[Doc Al]

part b

That was for part a. For part b, set up your equations for horizontal and vertical motion separately. The "trick" is to ensure that the vertical motion comes back to the starting point (y = 0) in exactly the time that the bullet travels the given horizontal distance. Set up the two equations and you can solve for θ.