Measuring Projectile Velocity Using Block Deviation

[Gavroy]

First of all: Sorry about my English, but I am from France ;-)
The problem:
Somebody shoots into a block which is put up on two free running ropes and now you want to determine the velocity of the projectile by measuring the deviation of the block. I also have to consider gravity, which may protect the block from being deviated and the projectile gets stuck to the block, if this is important.
I want to add that the mass of the projectile, the mass of the block and the length of the ropes are known.
I am sorry that I can’t offer you an initial stage for a solution. The only thing I know is that the conservation of momentum may be a possible approach

 

[tiny-tim]

Welcome to PF!

Hi Gavroy! Welcome to PF!

In questions like this, divide the motion into two stages, the collision and the swing …

i] in the collision, momentum is conserved, so find the final velocity for the collision, wchi becomes the initial velocity for the swing

ii] in the swing, (mechanical) energy is conserved