what is kinetic energy and how can we calculate kinetic energy before starting the lecture click on the subscribe button and get excels to our hundreds of conceptual lectures for free now what is kinetic energy well the word kinetic means motion we define kinetic energy as energy possessed by an object due to its motion for example consider a fast moving car it possesses kinetic energy due to its motion consider a fast moving by cycle it possesses kinetic energy due to its motion consider a fast moving football it also possesses kinetic energy due to its motion thus
from these three examples we learn that if an object is moving it possesses kinetic energy what happens to kinetic energy when an object stops are de stationary object possesses kinetic energy well kinetic energy purely depends upon the motion of an object when an object stops its kinetic energy becomes zero remember that when there is motion there is kinetic energy no motion means no kinetic energy let me repeat this important statement when there is motion there is kinetic energy no motion means no kinetic energy now let me give you one another example consider an airplane moving
above the earth it's certain height does it possesses kinetic energy well the answer is yes it possesses kinetic energy because it is in motion but it doesn't only possesses kinetic energy it also possesses gravitational potential energy due to the Earth's Pole remember that if we consider only this moving airplane and neglect the surrounding around it then this airplane only possesses kinetic energy but if we consider this moving airplane as well as its surrounding then it possesses both kinetic energy and potential energy let me elaborate this point more precisely consider a single moving charge and the
spheres we know that it is in motion and it possesses kinetic energy but this char possesses no potential energy now consider this same charge an electric field it possesses both kinetic energy and electric potential energy because the motion of this charge is affected by the electric field our electric force thus we learn that a moving body possesses kinetic energy but its potential energy purely depends upon its system our surroundings now let me teach you that what is the equation of kinetic energy well kinetic energy is equal to one-half M + 2 V squared for example
consider a moving truck let the mass M of this truck is 200 kg and the velocity V of this truck is 800 meter per second in this direction if we know the mass of an object and its velocity we can easily calculate its kinetic energy thus we simply plug in the value of mass and the value of velocity and this equation kinetic energy is equal to one-half 200 kg and 280 meter per second squared after calculation we get kinetic energy is equal to six point four times ten to the fifth joules thus the kinetic energy
of this truck is this much remember that the SI unit of kinetic energy is Joule and kinetic energy being energy is a scalar quantity also remember that if mass is given in grams and velocity and kilometer per R then always convert grams and 2 kg and kilometer per and to meter per second because a lot of students do this mistake while calculating kinetic energy finally let me teach you the most famous concept regarding kinetic energy for example if the speed of a car increases two times the kinetic energy changes by factor - well such type
of NC Q's are very common but they aren't difficult we know that kinetic energy depends upon mass and kinetic energy depends upon square of velocity if speed increases by two times kinetic energy increases by four times if speed increases by three times kinetic energy increases nine times similarly if speed increases by four times kinetic energy increases by sixteen times also remember that if speed decreases by two times kinetic energy decreases 1 upon 4 times if speed decreases three times kinetic energy decreases 1 upon ninth times and so on now what about the relationship of kinetic
energy and mass well it is very simple if mass increases by two times kinetic energy increases by two times if mass decreases by three times kinetic energy decreases by three times and so on I hope that you have learnt the concept of kinetic energy [Music]
