Determine the initial speed of the bullet

[mandy9008]

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

 

[kuruman]

Is there a question you wish to ask?

 

[collinsmark]

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?