CBSE Class 9 Answered
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
Expert Answer
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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