# Determine the initial speed of the bullet

## Homework Statement

An 8.00 g bullet is fired into a 160 g block that is initially at rest at the edge of a table of 1.00 m height. The bullet remains in the block, and after the impact the block lands d = 2.2 m from the bottom of the table. Determine the initial speed of the bullet.

## Homework Equations

y=voyt + 1/2 gt2
vox = x/t
mbvb = (mb + mB) v

## The Attempt at a Solution

y=voyt + 1/2 gt2
t2=-2(1m)/9.8 m/s2
t=0.45s

vox = x/t
vox = 2.2m / 0.45s
vox= 4.889 m/s

mbvb = (mb + mB) v
vb= ((0.008 kg + 0.160kg)/0.160kg) 4.889 m/s
vb=5.13 m/s

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kuruman
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Is there a question you wish to ask?

collinsmark
Homework Helper
Gold Member

Hello mandy9008,

## The Attempt at a Solution

y=voyt + 1/2 gt2
t2=-2(1m)/9.8 m/s2
t=0.45s
Your approach is good so far, , but be careful of your precision (significant digits). I think you should carry out your '0.45 s' term to a couple more digits here.
vox = x/t
vox = 2.2m / 0.45s
vox= 4.889 m/s

mbvb = (mb + mB) v
vb= ((0.008 kg + 0.160kg)/0.160kg) 4.889 m/s
vb=5.13 m/s
You're dividing by the mass of the block. Is that what you really want to do? 