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Question

What would be the momentum of the bullet and the gun before firing?

The correct answer is
The momentum of the bullet and the gun before firing would be zero

Momentum of Bullet and Gun Before Firing

The question asks about the momentum of the bullet and the gun before firing. Momentum is a fundamental concept in physics that describes the quantity of motion an object has. It is defined as the product of an object's mass and its velocity.

Mathematically, momentum ($\vec{p}$) is given by the formula:

$\vec{p} = m\vec{v}$

Where:

  • $m$ is the mass of the object
  • $\vec{v}$ is the velocity of the object

Momentum is a vector quantity, meaning it has both magnitude and direction.

Analyzing the State Before Firing

Consider the system consisting of the gun and the bullet inside it, just before the gun is fired. In this state:

  • The bullet is stationary relative to the gun.
  • The gun is typically held by a person or placed on a support, and assuming it's not moving, its velocity is zero.
  • Since the bullet is inside the stationary gun, the bullet's velocity is also zero relative to an external observer.

Therefore, before firing, both the bullet and the gun have zero velocity.

Calculating Momentum Before Firing

Using the momentum formula ($\vec{p} = m\vec{v}$):

  • For the bullet: Let $m_b$ be the mass of the bullet and $\vec{v}_b$ be its velocity before firing. Since $\vec{v}_b = 0$, the momentum of the bullet before firing is $\vec{p}_b = m_b \times 0 = 0$.
  • For the gun: Let $m_g$ be the mass of the gun and $\vec{v}_g$ be its velocity before firing. Since $\vec{v}_g = 0$, the momentum of the gun before firing is $\vec{p}_g = m_g \times 0 = 0$.

The total momentum of the system (bullet + gun) before firing is the sum of their individual momenta:

$\vec{p}_{total, before} = \vec{p}_b + \vec{p}_g = 0 + 0 = 0$

So, the total momentum of the bullet and the gun system before firing is zero.

Evaluating the Options

Let's look at the given options based on our analysis:

  1. The momentum of the bullet and the gun before firing would be zero. - This aligns with our calculation.
  2. The momentum of the bullet would be more than that of the gun. - This is incorrect as both have zero momentum before firing.
  3. The momentum of the gun would be more than that of the bullet. - This is incorrect as both have zero momentum before firing.
  4. Both would have certain velocity and so have the same momentum. - This is incorrect. Before firing, their velocity is zero, and therefore their momentum is zero. They would only have the same momentum if their mass and velocity were equal, which is not necessarily true even during firing (though the magnitude of momentum would be equal and opposite after firing).

Based on the principle of momentum and the state of the objects before firing, the momentum of both the bullet and the gun is zero.

The final answer is $\boxed{The momentum of the bullet and the gun before firing would be zero}$.

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Important Questions from Momentum and Energy

  1. Which among the following has the same dimension as that of energy?

  2. Light with an energy flux of 500 kW/m2 falls for 5 minutes at normal incidence on a non-reflecting circular surface with a radius of 10 cm. The total momentum delivered to this surface has a magnitude of ______.

  3. If the linear momentum of a moving object gets doubled due to application of a force, then its kinetic energy will

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