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Grade 12th passMechanics

How much applied force is needed to given an 8-N object (a) an upward acceleration
of 2 m/s2 and (b) a downward acceleration of 2 m/s2
? (c) In what direction must the latter
force act?

Profile image of joshua
6 Years agoGrade 12th pass
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1 Answer

Profile image of CHIRAG HIWAL
6 Years ago
(a) here we have force of 8N in downward direction and acceleration of 2m/s^2 in uppward. let we apply force F in upward direction. 
 Here,
mg=8N
mass of obj is 8/9.8 =0.816kg
So, by newton’s law of motion 
ma=F-mg
i.e. F= ma+mg
F=0.816*2+8=9.63N
 
(b) acc. 2m/s^2 uppward 
similarly,
ma=mg-F
i.e. F=8-2*0.816=6.37N
 
© when we apply both forces the block move upward.