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ICSE Class 9 Answered

 A motorbike running at 5m/s picks up a velocity of 30 m/s in 5 s.Calculate the acceleration  and  distance travelled during application of brakes ?
Asked by Vikas | 23 May, 2018, 12:15: AM
Expert Answer
i) Acceleration:
Velocity increases from 5 m/s to 30 m/s in 5 s.
Thus, u= 5m/s; v= 30 m/s; t=5 seconds 
By first law of equation of motion,
fraction numerator rightwards double arrow 30 minus 5 over denominator 5 end fraction equals a
rightwards double arrow a equals space 5 space m divided by s squared
ii) The distance travelled after the applications of brakes :
When brakes are applied, it causes deceleration
thus, a= -5m/s2 
And a motor bike will come to rest.
So, v=0 and u= 30 m/s 
Using third equation of motion
v - u2 = 2as 
distance travelled (s) is given by,
s equals space fraction numerator 0 minus space 30 squared over denominator 2 cross times left parenthesis negative 5 right parenthesis end fraction
s equals fraction numerator negative 900 over denominator negative 10 end fraction equals 90 space m space
So distance travelled after application of brakes is 90 metres. 
Answered by Shiwani Sawant | 23 May, 2018, 11:18: AM

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