Question 2: Define power and show that it is the dot product of force and velocity. What are the different units of power used in everyday life? Answer The amount of work done by a body in one second is called power. Mathematically, if W is the work done by a body in time interval ‘t’ seconds, then power ‘P’ is,Work as dot product of  and  Power is also related to the velocity of the object. In terms of velocity power is defined as Power is the scalar product of force and velocity. Consider a force  acting on a body through displacement  for a time interval of ‘t’ seconds. Then, W = . As , putting the value of W in the above equation, Hence power is related to the velocity and it is the dot product of force and velocity. Units of power In SI, unit of power is watt. watt is the power of a body that does work at the rate of one joule per second. Mathematically, Watt is a small unit and not suitable in case of large power generating and grid stations. The unit used in generating stations is mega watt. Multiples of watt in common use are, kilowatt and megawatt. 1 kilowatt = 10³ watts 1 megawatt = 10⁶ watts In British Engineering System (FPS), power is measured in horsepowers (hp). One hp is the power of an agency that does work at the rate of 550 foot-pound in one second. Conversion of SI and FPS is as 1 hp = 746 watts. Dimensions of power As power is