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CBSE Class 9 Answered

A body travels 200cm in the first 2 seconds and 220cm in the next 5seconds.Calculate the velocity at the end of the seventh second from the start​.
Asked by Santosh.kumar0317 | 27 Aug, 2019, 10:50: PM
answered-by-expert Expert Answer
Using 2nd equation of motion
s equals u t plus 1 half a t squared
200 equals u cross times 2 plus 1 half cross times a cross times 4 200 equals 2 u plus 2 a minus negative negative negative negative negative negative negative left parenthesis 1 right parenthesis
 
Distance travelled by the body in next 5 seconds is 220cm
So the total distance travelled by the body in 7 seconds = 200+220=420cm
420 equals u cross times 7 plus 1 half cross times a cross times 49 840 equals 14 u plus 49 a minus negative negative negative negative negative negative negative left parenthesis 2 right parenthesis
On solving equation (1) and (2)
 we get u=115cm/s 
a equals negative 16 c m divided by s squared
 
Velocity at the end of 7th  second is given by
v equals 115 plus open parentheses negative 16 close parentheses 7 v equals 3 c m divided by s
Answered by Utkarsh Lokhande | 28 Aug, 2019, 10:33: AM

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