A 0.22 LR-caliber bullet like that mentioned in Example 7.10 is fired into a door made of
Question:
A 0.22 LR-caliber bullet like that mentioned in Example 7.10 is fired into a door made of a single thickness of 1-inch pine boards. How fast would the bullet be travelling after it penetrated through the door?
Example 7.10
Determining a Stopping Force A bullet from a 0.22 LR-caliber cartridge has a mass of 40 grains (2.60 g) and a muzzle velocity of 1100 ft./s (335 m/s). It can penetrate eight 1-inch pine boards, each with thickness 0.75 inches. What is the average stopping forte exerted by the wood, as shown in Figure 7.13?
Figure 7.13. The boards exert a force to stop the bullet. As a result, the boards do work sal the bullet loses kinetic energy.
Strategy
We can assume that under the general conditions stated, the bullet loses all its kinetic energy penetrating the boards, so the work-energy theorem says its initial kinetic energy is equal to the average stopping force times the distance Penetrated. The change in the bullet's kinetic energy and the net work done slopping it are both negative, so when you write out the wink-energy theorem with the net-work equal to the average force times the stopping distance, that's what you get. The total thickness of eight 1-Inch pine bonds that the bullet penetrates is 8 ? ? in. = 6 in. = 15.2 cm.
Vector Mechanics for Engineers Statics and Dynamics
ISBN: 978-0073212227
8th Edition
Authors: Ferdinand Beer, E. Russell Johnston, Jr., Elliot Eisenberg, William Clausen, David Mazurek, Phillip Cornwell