Calculate KE of Projectile after Passing through Object.

[PotatoSmasher]

Hi I am new to the forums and currently studying year 12 physics. I was wondering is it possible to calculate the Kinetic Energy lost from a projectile, say a bullet, after passing through an object, say a piece of steel. I know the weight of the bullet (41.9g) and it's initial KE (17,820J). I also know the density of the steel (7.85 g/cc) and its thickness (5mm).

Note please this isn't a homework question, it's just for my own curiosity and expansion of my own knowledge. Many thanks :)

 

[tiny-tim]

Welcome to PF!

HI PotatoSmasher! Welcome to PF!

No, there's too many variables …

it depends on the shape of the bullet, amongst other things …

if you were in CSI, you'd find the answer by actually firing bullets at a sample of the metal …

that's really the only way ​

 

[sophiecentaur]

These are fun.

 

[PaulS1950]

Hi I am new to the forums and currently studying year 12 physics. I was wondering is it possible to calculate the Kinetic Energy lost from a projectile, say a bullet, after passing through an object, say a piece of steel. I know the weight of the bullet (41.9g) and it's initial KE (17,820J). I also know the density of the steel (7.85 g/cc) and its thickness (5mm).

Note please this isn't a homework question, it's just for my own curiosity and expansion of my own knowledge. Many thanks :)

All you need to do is measure the velocity of the projectile after it passes through the material and get its mass after you measure the velocity. Then it is Ek=1/2 MxV^2.
Paul

 

[PJC01]

Hello and welcome to the forums! It is definitely possible to calculate the Kinetic Energy (KE) lost from a projectile after passing through an object. In order to do so, we need to use the principle of conservation of energy, which states that energy cannot be created or destroyed, only transferred from one form to another.

In this case, the initial KE of the bullet before hitting the steel object can be calculated using the formula KE = 1/2 * m * v^2, where m is the mass of the bullet and v is its initial velocity. From the information provided, we can calculate the initial KE of the bullet to be 17,820J.

After the bullet passes through the steel object, some of its KE will be transferred to the object in the form of heat and sound energy. The amount of KE lost can be calculated by subtracting the final KE of the bullet from its initial KE. The final KE of the bullet can be calculated using the same formula, but with the final velocity of the bullet (which will be lower due to the resistance of the steel object).

To calculate the final velocity of the bullet, we need to consider the energy lost due to the bullet's deformation and the energy required to penetrate the steel. This can be calculated using the formula KE = 1/2 * k * x^2, where k is the spring constant and x is the distance the bullet was deformed. This energy will be subtracted from the initial KE of the bullet to get the final KE.

Once we have the final KE, we can use the same formula to calculate the final velocity of the bullet. From there, we can calculate the KE lost by subtracting the final KE from the initial KE.

I hope this helps and satisfies your curiosity. Keep up the good work in your physics studies!