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CBSE Class 9 Answered

An object starting from rest travels 20 m in first 25s and 160 m in next 4s. What will be the velocity after 7s from the start?
Asked by Aryan Suresh | 24 Jun, 2013, 05:06: PM
answered-by-expert Expert Answer
The object starts from rest and travels 20m in first 25 sec. 
 
Hence, u = 0, t= 25 and s = 20m

Using second law of motion
s = ut+1/2at^2 
20 = 0*25 + 1/2*a*25*25
20 = 1/2*a*25*25
a = 40/625 m/s^2
 
Now, using the first law of motion to compute velocity after 7 sec from start, t in this case would be 7 sec
 
v = u+at
v = 0 +40/625*7
v = 280/625
v = 0.45 m/s
Answered by | 25 Jun, 2013, 04:23: PM

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