Bullet Hits Block Attached to Spring What am I doing wrong?

[sweetpete28]

A wooden block of mass M = 1.83 kg is rest on a frictionless, horizontal table attached to the end of an unstretched spring (k = 217 N/m). A bullet of mass m = 8.02 g is fired horizontally into the block at speed vo = 394 m/s. The bullet comes to rest inside the block, and causes the mass to oscillate on the spring. If there is no friction between the block and the table: find A, the amplitude of the resulting oscillation. You can assume the mass never hits the wall (to which the spring is attached.)

Here is what I did, and I really don't see how this is wrong...

By conservation of momentum --> m1v1 = (m1 + m2)v2
(.0082)(394) = (1.83 + .0082)v2
v2 = 1.75759m/s

1/2mv^2 = 1/2kA^2

(1/2)(1.83802)(1.75759)^2 = (1/2)(217)A^2

A = .162m


How is this wrong??

 

[gneill]

Check the mass value for the bullet that you used in the calculation of v2.

 

[ehild]

A wooden block of mass M = 1.83 kg is rest on a frictionless, horizontal table attached to the end of an unstretched spring (k = 217 N/m). A bullet of mass m = 8.02 g is fired horizontally into the block at speed vo = 394 m/s.

By conservation of momentum --> m1v1 = (m1 + m2)v2
(.0082)(394) = (1.83 + .0082)v2
v2 = 1.75759m/s

You dropped a zero from the mass of the bullet.

ehild