Bullet penetrating a block problem

In summary, a 10g bullet fired from a rifle with a barrel length of 60 cm at a horizontal speed of 400 m/s penetrates a block of wood to a depth of 12 cm. Using kinematic equations, the bullet's acceleration while inside the block can be determined to be -6.7*105. When attempting to find the time it takes for the bullet to come to rest using the equation X= Vit + 1/2 at^2, it results in a function with no real roots. However, there may be other kinematic equations that can be used to solve for the time.
  • #1
mjolnir80
55
0

Homework Statement


a rifle with a barell length of 60 cm fires a 10g bullet with a horizontal speed of 400 m/s. the bullet strikes a block of wood and penetrates to a depth of 12 cm. how long does it take the bullet to come to rest( from when it penetrates the block to when it stops)?



Homework Equations


kinematic equations


The Attempt at a Solution


we can figure out the acceleration of the bullet while its in the block with
Vf2= Vi2 + 2aX which gives -6.7*105

but now when i try to use X= Vit + 1/2 at2 to figure out time it give me a function with no real roots
what am i doing wrong here?
 
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  • #2
Any other kinematic equations you may have overlooked?
 
  • #3
dont worry i haven't forgotten about the other equations :)
i was just wondering why this one didnt work
 
  • #4
I get a real, double root when I solve it using your method, so you must be making an error somewhere in your work...If you actually post your work, I can point it out to you. :wink:
 
  • #5
oops guess i better double check that
thanks for the help :biggrin:
 

Related to Bullet penetrating a block problem

1. How does the speed of the bullet affect its ability to penetrate a block?

The speed of the bullet plays a crucial role in its ability to penetrate a block. The faster the bullet travels, the more kinetic energy it has, which results in a greater force upon impact. This force allows the bullet to penetrate deeper into the block.

2. What factors besides speed can affect a bullet's ability to penetrate a block?

Besides speed, other factors that can impact a bullet's ability to penetrate a block include the shape and density of the bullet, the material and thickness of the block, and the angle at which the bullet hits the block.

3. Can a smaller bullet penetrate a block better than a larger bullet?

In most cases, a smaller bullet will not be able to penetrate a block better than a larger bullet. This is because a larger bullet has more mass and therefore more kinetic energy, giving it a greater ability to penetrate through obstacles.

4. How does the angle of impact affect a bullet's penetration of a block?

The angle of impact can greatly affect a bullet's penetration of a block. When a bullet hits a block at a perpendicular angle, it is more likely to penetrate deeper than if it hits at an oblique angle. This is because the force of impact is more concentrated when the bullet hits directly perpendicular to the surface.

5. What materials are most effective at stopping a bullet from penetrating a block?

The most effective materials for stopping a bullet from penetrating a block are those that are dense and have a high tensile strength. Materials like steel, concrete, and Kevlar are commonly used for bulletproof barriers and have proven to be effective at stopping bullets from penetrating through them.

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