1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Bullet hitting a wood block in a vise. Find initial velocity?

  1. Nov 5, 2013 #1
    1. The problem statement, all variables and given/known data
    A 7.00 g bullet, when fired from a gun into a 1.10 kg block of wood held in a vise, penetrates the block to a depth of 6.40 cm. This block of wood is next placed on a frictionless horizontal surface, and a second 7.00 g bullet is fired from the gun into the block. To what depth will the bullet penetrate the block in this case?

    2. Relevant equations
    vf^2 = vi^2 + 2ad
    p = mv
    m1v1i + m2v2i = (m1+m2)vf
    Δp = ƩF dt

    3. The attempt at a solution
    Honestly, I'm pretty baffled. I can't do anything with momentum without an initial velocity, and I can't find that without acceleration or time. I've seen some other posts that talk about resistive force, but we haven't discussed that so I don't think that's necessary. I think the vise is what's throwing me for a loop. It's inelastic, so there no conserved energy. I'm just not sure what the first step is.
  2. jcsd
  3. Nov 5, 2013 #2

    Simon Bridge

    User Avatar
    Science Advisor
    Homework Helper

    It's a comparison between the vise and the free block.
    This is one of those situations where you have to write down a bunch of simultanious equations.

    You know that momentum is conserved.

    You know the relationship between kinetic energy and momentum.

    You know the relationship between work and change in energy, also work and force.

    You also know a bunch of kinematic equations and newtons laws.
    Last edited: Nov 5, 2013
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted

Similar Discussions: Bullet hitting a wood block in a vise. Find initial velocity?
  1. Bullet hitting wood (Replies: 4)