A heavy body of mass `25kg` is to be dragged along a horizontal plane (`mu` = `(1)/(sqrt(3))`. The least force required is `(1 kgf = 9.8 N)`

Options

A. 25 kgf
B. 2.5 kgf
C. 12.5 kgf
D. 6.25 kgf

Answer

C

Explanation

Let the body is acted upon by a force at an angle `theta` with horizontal.
FBD:
`Fcostheta=mu9mg-Fsintheta)`
`impliesF=(mumg)/(costheta+musintheta)`
For min. force: `(costheta+musintheta)` should be max.
`implies-sintheta+mucostheta=0`
`impliestantheta=mu` or `theta=tan^-1((1)/(sqrt3))=30^@` substituting
`F_(min)=12.5kgf`