Kinematics Problem on a bullet

[frozen7]

A rifle is aimed horizontally at the centre of a large target 200m away. The initial speed of the bullet is 500 m/s.
(a) Where does the bullet strike the target?
(b) To hit the centre of the target, the barrel must be at an angle above the line of sight. Find the angle of elevation of the barrel.

What does (a) mean actually? And can anyone draw out the diagram ? Thanks.

 

[Nylex]

Part a. is asking for how far below the centre of the target the bullet hits I think. It's a projectile motion problem.

 

[frozen7]

The how to calculate the value? since we just know how far is the target beyond the rifle.

 

[Dr.Brain]

(a) If the bullet is aimed directly at the centre of the target and bullet is let out , it will eventually start falling with gravity and will hit a point below the target.Simple projectile motion problem.

BJ

 

[Nylex]

The how to calculate the value? since we just know how far is the target beyond the rifle.

You can work out the time it takes to travel that distance horizontally, then find the vertical distance traveled in the same time.

 

[frozen7]

does it mean displacement in y-compenent is the value this question ask for?

 

[Dr.Brain]

Yes.

BJ

 

[frozen7]

And how to solve the (b) question?

 

[Dr.Brain]

So that you don't miss the target , you need to raise your gun up making some angle with horizontal.Calculate that angle.

BJ

 

[HallsofIvy]

The point is that, in order to do this problem, you should have formulas relating the horizontal and vertical distance to time, initial speed, acceleration due to gravity. What formulas do you have to use?