Momentum Conservation: Bullet enters a block

In summary, momentum conservation is a fundamental principle in physics that states the total momentum of a closed system remains constant. This means that in any interaction or collision, the total initial momentum must equal the total final momentum. When a bullet enters a block, the total initial momentum of the system is equal to the bullet's momentum before the collision and the principle of momentum conservation can be used to calculate the velocity of the bullet and block after the collision. While it may seem like momentum is not conserved, it is a fundamental law of physics and can never be violated, even though external forces may affect its apparent conservation.
  • #1
Shreya
188
65
Homework Statement
I am not able to solve the second part of the question.
Please refer the image below.
V refers to the final velocity after collision, v is the initial velocity of bullet. L is the length of string and h is the height that the block rises to.
Relevant Equations
Conservation of Momentum
I can understand that using conservation of momentum, we can find v. But we need V for that. The equation for V involves h and so we need h. But I am not able to comprehend the equation involving l,h and a. The question doesn't specify what a is.
Please be kind to help
 

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  • #2
That’s just Pythagoras’ theorem.
$$
l^2 = (l-h)^2 + a^2
$$
Expand the (l-h) square and cancel ##l^2## on both sides.
 
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  • #3
Orodruin said:
That’s just Pythagoras’ theorem.
Thanks @Orodruin! I get it now.
 
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FAQ: Momentum Conservation: Bullet enters a block

What is momentum conservation?

Momentum conservation is a fundamental principle in physics that states that the total momentum of a system remains constant unless acted upon by an external force. This means that in a closed system, the total momentum before an event must be equal to the total momentum after the event.

How does momentum conservation apply to a bullet entering a block?

When a bullet enters a block, the total momentum of the system (bullet + block) before the collision is equal to the total momentum after the collision. This means that the momentum of the bullet is transferred to the block upon impact, causing the block to move with the same velocity as the bullet before the collision.

What factors affect momentum conservation in this scenario?

The main factors that affect momentum conservation in this scenario are the mass and velocity of the bullet and the block. The greater the mass and velocity of the bullet, the greater the momentum it will transfer to the block upon impact. Additionally, the type of material the block is made of can also affect momentum conservation.

Is momentum conserved in an elastic collision between a bullet and a block?

Yes, momentum is conserved in an elastic collision between a bullet and a block. In an elastic collision, the total kinetic energy of the system is conserved, meaning that the bullet and block will both continue to move with the same velocity after the collision as they did before.

How is momentum conservation related to the law of conservation of energy?

Momentum conservation is closely related to the law of conservation of energy. Both principles state that in a closed system, the total amount of a physical quantity (momentum or energy) remains constant. In the case of a bullet entering a block, the energy of the system is conserved as the kinetic energy of the bullet is transferred to the block upon impact.

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