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Sample Hlab Report

# Sample Hlab Report - Sample Write-up Physics 99999 Lab 3...

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Sample Write-up Physics 99999, Lab 3 September 34, 2008 Joe Student Lab Partners: Julie Etudiant, Atru Schola Purpose: We are asked to determine the speed of a 0.22 caliber bullet as accurately as possible. This could be useful in forensic investigations, where the speed of the bullet may determine how much damage is done, or gun design, where the objective may be to reach a given muzzle velocity, for example. Background : The measurement of velocity can usually be reduced to a measurement of the time required to pass between two known points: v=d/t, assuming that the velocity is constant (a good approximation in this case). However, given the extreme speed of the bullet, this was not practical in this case. We guess that the bullet's speed is about 100m/s, which means it would only take .2s to cross the lab if the lab is about 20 meters long. The photogates only have a timing resolution of about 40ms, so, this would lead to something like a 30% error on the velocity. Instead, we chose to create a collision, so that the momentum of the bullet was transferred to that of a stationary object. We chose a heavy object so that its velocity was much smaller than that of the bullet, making it much easier to measure. So, the underlying principle we used was conservation of momentum. This was a totally inelastic collision, since the bullet was imbedded in the object after the collision. So, our equation is: pi = pf; mV = (m+M)v where m is the mass of the bullet, V is the bullet's initial velocity, which we wish to measure, M is the mass of our target object, and v is the final combined velocity.

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Sample Hlab Report - Sample Write-up Physics 99999 Lab 3...

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