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Mechanics M1 problem-help needed with constant acceleration

Posted by White Group Mathematics on March 10, 2015 at 2:20 AM


Hi,


 

The question asks,


 

A body moving in a straight line with constant acceleration takes 3 sec and further 5 sec to cover two successive distances of 1m. Find acceleration.(Hint: use distances of 1m and 2m from the start of motion)


 

I cannot seem to figure out how to solve this. Could you please show the calculations to get the same answer presented in the book, which is -1/30 m/s^2 ?


 

Thanks.




Student X










Let us use s=ut+1/2 * at^2


 

When the first metre is covered, substituting s=1 and t=3 gives

 

3u+ 9a/2 = 1 -----------------(1)



 

When the first two metres are covered, substituting s=2 and t= 3+5=8 gives

 

8u+ 32a = 2 ====> 4u+16a =1 -------(2)



 

Solve these two equations simultaneously, you should be able to retrieve the answer for the acceleration shortly.



 

Peace.



Best Regards,

Mr Koh


Categories: Math Queries

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