You have been asked to design a "ballistic spring system" to measure the speed of bullets. A bullet of mass 6.20 g is fired into a block of mass 2.10 kg. The block, with the embedded bullet, then slides across a frictionless table and collides with a horizontal spring whose spring constant is k=63.0 N/m. The opposite end of the spring is anchored to a wall. What was the speed of the bullet if the spring's maximum compression is 12.1 cm?
The Attempt at a Solution
m1= bullet and m2= block; v1= vbullet
i first solved m1v1+m2v2= mtotal*vfinal for Vfinal..so that looked like vfinal= m1*v1/mtotal
then i used the energy equations to get 0.5*k*x2= 0.5*m*v2
in v2 i substituted m1*v1/mtotal
and then tried to solve for v1 which is the speed of the bullet we are looking for ...and my hwk app. is telling me my answer is wrong...so i was wondering if i made a mistake in the workings somewhere..