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Question
55:
55 A body starts from rest with an accelerat ion a , after 2 second , another body B status from rest with an acceleration a2. If they travel equal distance in the 5th second. after the start of A, then the ratio a1 : a2 is equal to:
(A) 5:9 (B) 5:7
(C) 9:5 (D) 9:7
55 A body starts from rest with an accelerat ion a , after 2 second , another body B status from rest with an acceleration a2. If they travel equal distance in the 5th second. after the start of A, then the ratio a1 : a2 is equal to:
(A) 5:9 (B) 5:7
(C) 9:5 (D) 9:7
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Solution
Dear Student ,
For the body ‘A’, the distance travelled in 5th second is,
S5 = 0 + ½ a1 (2n - 1)
=> S5 = 9/2 a1 [n = 5]
For the body ‘B’, the distance travelled in the 5th second after the start of A is actually the distance travelled by the body B in the 3rd second, since, B starts 2 s later.
Therefore,
S3 = 0 + ½ a2 (2n - 1)
=> S3 = 5/2 a2 [n = 3]
Since, the distance travelled are same,
9/2 a1 = 5/2 a2
=> a1 : a2 = 5 : 9
Regards
Dear Student ,
For the body ‘A’, the distance travelled in 5th second is,
S5 = 0 + ½ a1 (2n - 1)
=> S5 = 9/2 a1 [n = 5]
For the body ‘B’, the distance travelled in the 5th second after the start of A is actually the distance travelled by the body B in the 3rd second, since, B starts 2 s later.
Therefore,
S3 = 0 + ½ a2 (2n - 1)
=> S3 = 5/2 a2 [n = 3]
Since, the distance travelled are same,
9/2 a1 = 5/2 a2
=> a1 : a2 = 5 : 9
Regards
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