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

Dear Student ,
For the body ‘A’, the distance travelled in 5
th 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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Hiii
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5:7
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9:7
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I think it's 5:7
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