You multiply by 2 to clear the fraction - this makes it easier to solve. If it helps think of it as dividing both sides by 1/2 which is the exact same thing
OK I'm a bit lost. Why in this equation do we multiply both sides of the equation by 2? Where does the 2 come from? I can see that I should try to make v the subject, and I can see the logic of dividing both halves of the equation by m, but multiplying both halves by 2 seems a completely arbitrary thing to do. Can someone please help me work through this equation and try to help me to understand it?