Two forces each of magnitude F, have a resultant of the same magnitude F. The angle between the two forces is

Physics with Akhtiar Ali  Bullo

Two forces each of magnitude F, have a resultant of the same magnitude F. The angle between the two forces is Physics class 11 mcqs  Vectors mcqs  First year physics mcqs

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00:00the question is two forces each of magnitude F have a resultant of the same

00:10magnitude F the angle between the two forces is a 45 degree b 120 degree c 150

00:21degree d 180 degree by using law of cosine R is equal to under root f1

00:40square plus f2 square plus 2f1 f2 cos theta here's f1 is equal to f2 is equal

01:04to F and also resultant is equal to F so by placing the values F is equal to

01:18under root f1 square means f square plus f2 square means f square plus 2f into f

01:31cos theta so F will be equal to under root f square plus f square it will be

01:422f square plus 2f into f f square cos theta so to remove square root squaring

01:54on both sides so f square will be equal to 2f square plus 2f square cos theta

02:08here's plus 2f square so when we will take it on the other side of equal then

02:16it will be minus 2f square so f square minus 2f square is equal to 2f square cos theta

02:27so plus f square minus 2f square so it will be minus f square is equal to 2f square cos

02:39theta as we have to find angle so 2f square cos theta is equal to minus f square so cos

02:53theta will be equal to minus f square upon 2f square so f square will be get cancelled

03:00with f square so theta will be equal to cos inverse minus 1 upon 2 is the value of cos

03:10inverse minus 1 upon 2 is 120 degree so the correct option will be b 120 degree.

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