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
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.