Spring launched ball in barrel

1. Oct 20, 2007

pinkyjoshi65

A BB gun fires a 8.24-g projectile by using a compressed spring (k = 2.88 × 103 N/m) and a 15.1 cm long barrel. As the disc travels through the barrel, it experiences a constant frictional force of 0.125 N. If the spring is compressed 16 mm, what is the speed of the BB as it leaves the gun?

So now we know that the Force is kx= 2.88*103*0.016= 4.74N

so..we use F=ma and find a.

then i got stuck..

2. Oct 22, 2007

$$\frac{1}{2} mv^{2} = \frac{1}{2} kx^{2} - Fs$$