What is a frame of reference in Class 11 Physics Chapter 3 Motion in a Straight Line and why is it essential in describing motion?

Yes, there are many numerical problems in class 11 Physics. All important formulas must be on figure tips.

Class 11 Physics Chapter 11 is Thermodynamics. It is one of the most important topic in Physics. 

There are three main processes Isothermal, adiabatic and cyclic process. In isothermal, the system is thermally conductive and the temperature remains constant. In adiabatic process, the system is thermally isolated and there is no change in heat temperature. The system returns to its initial stage

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Let us consider a vector $\stackrel{?}{P}$ . The equation can be written as

Px = Py = 1 $\left|\stackrel{?}{P}\right|$ = $\surd (P_x^2+P_y^2)$ $\left|\stackrel{?}{P}\right|$ = $\surd (1^2+1^2)\left|\stackrel{?}{P}\right|$ = $\sqrt{2}$ …….(i)

So the magnitude of vector $\stackrel{?}{i}$ + $\stackrel{?}{j}$ = $\sqrt{2}$

Let $\theta$ be the angle made by vector $\stackrel{?}{P}$ , with the x axis as given in the above fi