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**bullet and pendulum bob....initial speed...help! momentum.**

**1. The problem statement, all variables and given/known data**

An 7.0 g bullet is fired into a 3.5 kg pendulum bob initially at rest and becomes embedded in it. If the pendulum rises a vertical distance of 8.0 cm, calculate the initial speed of the bullet.

________m/s

**2. Relevant equations**

well there's many ways to do it, but heres one way:

v=sqrt((1+M/m)*2gh)

i tried it another way too, and got the same answer that i did with the above equation

**3. The attempt at a solution**

so first, 7g bullet = .007kg bullet and height of 8cm = .08m

ok so then v=sqrt((1+3.5/.007)*2*9.8*.08) = ~28.03 m/s

now, i tried this TWO WAYS and got the same answer.

but webassign says it's wrong.

why?