Converting EV to kg-m/s: A Step-by-Step Guide

[gnome]

I'm having a hard time getting used to expressing quantities in electron-volt equivalent units.

Masses and energies expressed as MeV/c² are confusing, but manageable.

But I seem to have a complete mental block over momentum as MeV/c. It's easy enough to look at a table & see that 1 MeV/c = 5.344 x 10^-22 kg-m/s, but could someone please walk me (or drag me ) through the derivation of that conversion?

 

[quantumdude]

The units of momentum are those of energy over speed.

(1 Joule/m/s)=(1 J*s/m)*(1eV/1.6*10^-19J)*(3*10⁸(m/s)/1c)

Cancel the units, crunch the numbers, and you'll have it.

 

[M98Ranger]

Converting from electron-volt (eV) to kilogram-meter per second (kg-m/s) can be confusing at first, but with a step-by-step guide, it can become easier to understand. Let's break down the process together.

Step 1: Understand the Units

First, it's important to understand the units we are working with. Electron-volt (eV) is a unit of energy, while kilogram-meter per second (kg-m/s) is a unit of momentum. Momentum is defined as the product of mass and velocity, so it can be expressed as kg-m/s.

Step 2: Use the Equation E=mc^2

The equation E=mc^2, where E is energy, m is mass, and c is the speed of light, is a fundamental equation in physics. This equation tells us that energy and mass are equivalent and can be converted into each other.

Step 3: Convert from eV to Joules

Since we know that 1 eV is equal to 1.602 x 10^-19 Joules, we can convert eV to Joules by multiplying the given value by 1.602 x 10^-19.

Step 4: Use the Equation p=E/c

The equation p=E/c, where p is momentum, E is energy, and c is the speed of light, tells us that momentum is equal to energy divided by the speed of light. This equation is derived from the equation for kinetic energy, which is 1/2mv^2, where m is mass and v is velocity.

Step 5: Plug in the Values

Now, we can plug in the values we have and solve for momentum. Let's say we have an energy of 1 MeV (1 million eV). We first convert this to Joules by multiplying by 1.602 x 10^-19 to get 1.602 x 10^-13 Joules. Then, we divide by the speed of light, which is approximately 3 x 10^8 m/s. This gives us a momentum of 5.344 x 10^-22 kg-m/s.

Step 6: Practice and Familiarize Yourself

The more you practice converting from eV to kg-m/s, the more comfortable you will become with the process. It may also be helpful to create a conversion chart or use online calculators to check your work.

In conclusion, converting