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XI-3-1 Rest and Motion
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In physics how do we declare things are at rest or in motion? it is described in this lesson..

Pradeep Kshetrapal is teaching live on Unacademy Plus

Pradeep Kshetrapal
State topper in school exams, selected in IIT Kharagpur, M.Sc., 30 yrs in teaching.

Unacademy user
sir bohut acca laga apka video dakkor thanks sir
sir aap to hr jgh great ho utube m unacademy hmare dil m hr jgh...
  1. PHYSICS By Pradeep Kshetrapal

  2. Class XI Chapter 3 Motion in Straight Line Topic: Rest and Motion Lesson XI-3-1 Pradeep Kshetrapal

  3. MOTION means continuously changing ones position.

  4. Every thing in this universe is in the condition of motion, as the universe is expanding 4

  5. When we are sleeping, we are in state of motion as the earth is rotating

  6. Earth is not only rotating about its own axis but also revolving around Sun

  7. Then how do we define object at REST

  8. First lets be introduced with two terms Surrounding and frame of reference. Surrounding: The material or radiation in neighbourhood is called surrounding. We can also name it as 'Frame of Reference'. And every individual thing in that is a constituent or member of that Frame of reference.

  9. Particle at Rest: An object which is not changing it's position with respect to surrounding is taken as at rest for practical purpose.

  10. I am continuously moving as l am on surface of earth, but with respect to my room, walls, floor, furniture, I am not changing my position so l can declare that l am at rest ( w.r.t. surface of earth.) boun d 10

  11. MOTION: An object which is continuously changing its position with respect to surrounding is said to be in motion. We can also say that it is in motion with respect to THAT particular surrounding. 12

  12. Here earth is moving w.r.t. Sun, We can declare that, because distance between Sun and Earth is changing continuously 14

  13. A person travelling by train is: Rest in relation to his co-passengers and berths, floor of the coach. 2. In motion in relation to another person standing at the platform and seeing the train moving i.e. In relation to platform he is moving. 17

  14. In the next lecture we see what is considered a point mass in Physics of motion. 18