If #µ = 0.40# and #mg = 20N#, what minimum force F will keep the box from falling?

a. #100N#
b. #80N#
c. #50N#
d. #20N#

1 Answer
Mar 4, 2018

Answer:

#c. 50N#

Explanation:

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Considering the arrangement to be as follows,

So,here frictional force will be acting upwards so that it can balance the weight of the box,now we need to apply #F# such that it will help the frictional force just to balance the weight of the box,on applying much force the box will accelerate upwards.

So,we can write, #f=mg=20#

and,frictional force acting is #mu N=muF=0.40F# (as, #F=N#)

So,we can equate to write,

#0.40F=20#

or, #F=50N#

So, #c. 50N# will be the answer.