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A plank with a box on it at one end is g...

A plank with a box on it at one end is gradually raised about the other end. As the angle of inclination with the horizontal reaches `30^(@)` , the box starts to slip and slides 4.0 m down the plank in 4.0 s. The coefficients of static and kinetic friction between the box and the plank will be repectively.

A

0.4 and 0.3

B

0.6 and 0.6

C

0.6 and 0.5

D

0.5 and 0.6

Text Solution

Verified by Experts

The correct Answer is:
C
`mu_(s)=tan30^(@)=(1)/(sqrt(3))=0.57~~0.6`
`S=ut+(1)/(2)at^(2)`
`4=0+(1)/(2)(gsin30^(@)-mu_(k)cos30^(@))(4)^(2)`
`0.5=10xx(1)/(2)-mu_(k)10xx(sqrt(3))/(2)`
`5sqrt(3)mu_(k)=4.5`
`mu_(k)=0.51`
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