(adsbygoogle = window.adsbygoogle || []).push({}); 1. The problem statement, all variables and given/known data

A 10g bullet strikes and becomes embedded in a 0.200kg block of wood placed on a horizontal surface just in front of the gun. If the coefficient of sliding friction between the block and the surface is 0.4 and the impact drives the block a distance of 8m before it comes to rest, what is the velocity of the bullet before it strikes the block of wood?

2. Relevant equations

E(kinetic)=E(frictional)

1/2(m1+m2)v2^2=μ(m1+m2)gs

or

ma=μmg

a=μg

v^2=u^2+2as

v1(m1)=v2(m1+m2)

3. The attempt at a solution

I've tried 2 different ways to do it which are:

1.)

m1=0.010kg

m2=0.200kg

s=8m

μ=0.4

1. E(kinetic)=E(frictional)

1/2(m1+m2)v^2=μ(m1+m2)gs

1/2(0.210)v^2=0.4(0.210)(9.8)(8)

v2=7.92m/s

m1v1=(m1+m2)v2

0.010v1=0.210*7.92

v1=166.32m/s

2.)

ma=μmg

a=μg

a=0.4*9.8

a=3.92

v^2=0

a=-3.92

s=8m

u^2=?

v^2=u^2+2as

0=u^2+2(-3.92)(8)

u^2=7.92

m1v1=(m1+m2)v2

0.010v1=0.210*7.92

v1=166.32m/s

I'd love to know if I'm on the right track here. Thanks a million in advance.

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# Speed Of A Bullet Before It Strikes A Block Of Wood

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