When it comes to firearms, trying to understand the underlying principles can be confusing. Is it just the Momentum or also the Kinetic energy which is responsible for the damage caused by a bullet? Let's dig out the truth ..
In this article, you will learn an important principle that applies to firearms. 🔫
Imagine getting struck by 2 fast moving objects having the same momentum. One object weighs 10 Kg & the other one weighs 0.1 Kg.
Which object would cause more damage?
Of course! Both would cause equal damage as their momentum is equal.
This was intuitive. Right?
As it turns out, the 0.1 Kg object causes more damage! 😮
Surprised? Let's see how..
The momentum of a particle is given by P = mv
The Kinetic energy is given by KE = ½ mv^2
If we substitute the equation for momentum above we get,
KE = (1/2) P^2/m
Since ‘m’ is in denominator, the KE is larger for smaller m, with P held constant.
Therefore, the object weighing 0.1 Kg will have a lot more Kinetic energy than the object weighing 10 Kg.
When a bullet leaves a gun it has same momentum as the gun, due to conservation of momentum. But, the bullet has much more Kinetic energy than the gun!
Here are some things you should know about Kinetic Energy and Momentum:
Are momentum and Kinetic energy same?
The momentum and kinetic energy are not the same as momentum is a vector (has a direction) and kinetic energy is a scalar (does not have a direction). Momentum also increases linearly with velocity while kinetic energy increases quadratically, so their values are not the same at higher velocities.
Why is momentum a vector while Kinetic energy scalar?
Kinetic energy is considered a scalar as it describes the total energy associated with motion, meaning that kinetic energy does not have any particular direction in space. Meanwhile, momentum describes motion in a specific direction, meaning that it has a different value in each special direction.
Kinetic energy is typically more useful in problems where the direction of motion doesn’t matter, while momentum is more useful when describing motion in different directions.
Momentum is more useful if we want to determine which way an object is moving (such as when a force is applied and we want to know which way the object will begin moving).
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