- #1

- 158

- 10

- Homework Statement
- Find velocity with vector or without vector

- Relevant Equations
- vector

At the moment he wrote that ##\frac{1}{2}mv_2^2=\frac{1}{2}m(-\dot{y}+\dot{x})^2##

But, I know from vector ##v_2=\sqrt{(-\dot{y})^2+(\dot{x})^2}##. At first I (he) found that ##v_2=-\dot{y}+\dot{x}##. But, when thinking of simple velocity in ##x## and ##y## coordinate then I get $$v^2=\dot{x}^2+\dot{y}^2$$ (I remember the equation from my last book). What am I taking wrong with the top (absolute top) equation?

In the equation, ##v_2=\sqrt{(-\dot{y})^2+(\dot{x})^2}## if I square both side than I get the equation which I gave above. So, can we write that ##v=\dot{x}+\dot{y}##. Then, if we square both side than that's simple algebraic expression. Maybe, this time I am mixing Algebra with Vector this time.