A bullet of mass 7.00 g is fired horizontally into a wooden block of mass 1.29 kg resting on a horizontal surface. The coefficient of kinetic friction between block and surface is 0.180. The bullet remains embedded in the block, which is observed to slide a distance 0.230 m along the surface before stopping.(adsbygoogle = window.adsbygoogle || []).push({});

What was the initial speed of the bullet?

Okay, first off, I know the block is sliding after the collision so that is internal energy.

[tex]\Delta[/tex]U_{internal}= Friction Force* Distance

=(12.7106N)(.180)(.230m) = 0.52621884J

From here, i do not know what to do.

Here was what I attempted:

KE=[tex]\Delta[/tex]U_{internal}

so

.5(1.297kg)v^2 = 0.52621884J

Velocity of the block was 0.9007m/s

Then I used Conservation of Momentum

Pi = Pf

.007kgV = (1.297kg)(.9007m/s)

V=166.9m/s

I don't know, seems slow for a bullet.

**Physics Forums | Science Articles, Homework Help, Discussion**

Dismiss Notice

Join Physics Forums Today!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

# Homework Help: A bullet and a block (Momentum)

**Physics Forums | Science Articles, Homework Help, Discussion**