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If a body covers 200cm in first 2 seconds and 220 CM in next 4  seconds then what is the value of N if at the last of 7th second a body has a velocity of 2N centimetre per second
Asked by Aryangupta2440 | 10 May, 2019, 11:13: AM
Formulas to be used :-  S = ut + (1/2)at2   and  v = u+at  ,
where S = distance travelled, u is initial speed, t is time, a is cm/s2 and v is final speed

Let the initial speed u cm/s and acceleration is  a   cm2/s .

distance travelled in first 2 seconds, S2 = 2u + (1/2)a×4  = 2( u + a ) = 200 cm  or  u + a = 100  ..................(1)
speed after 2 seconds,   u2 = u+2a  cm/s

distance travelled in next 4 seconds = (u+2a)4 + (1/2)a×16  = 4(u+4a) = 220 cm  or  u + 4a = 55 ..............(2)

By solving eqns.(1) and (2),  we get a = -15 cm/s2   and  u = 115 cm/s

speed at 7th second , u7 = 115 -15×7 = 10 cm/s

Hence 2N= 10 cm/s  or  N = 5 cm/s
Answered by Thiyagarajan K | 10 May, 2019, 01:22: PM

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