A block slides down an inclined surface of inclination 30 degrees with horizontal .Starting from rest it covers 8 M in first two seconds.find the coefficient of kinetic friction between the two.
please tell the question with detailed steps and tell me the basics of this question also.Please tell fast

2
is tghe block sliding with acceleration?
not tghe it is the

Answers

2014-10-12T09:36:48+05:30

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See diagram.

let the coefficient of kinetic friction = μ.      Frictional force Ff acts upwards along the inclined surface.      Ff = μ * Normal reaction N

Since the block is not moving perpendicular to the incline. So forces arebalanced in that direction.
                            mg Cos 30° = N
           So Ff = μ * N = μ * m * g Cos 30°

Resultant Force along the incline downwards :   mg Sin 30° - Ff
                so mass m * acceleration a  = m g 1/2 - μ * m * g √3 /2 
                           a =  (1 - μ √3) * g/2

let g = 10 m/sec²

formula for distance traveled along the incline:  s = u t + 1/2 a t²
 
             8 meters = 0 + 1/2 [ (1 - μ √3) * 10/2 ]  *  2²
                8 = 10 (1 -  μ √3)
              
                    1 - μ √3  = 8/10 = 0.8
                      μ √3  = 0.2

                    μ = 0.1155
           


0
please sir
sir exams are approching
wait. let me see
3 * square root of 3/5 ??? it cannot be.. it is more than 1. coefficient of friction is usually less than 1.
mu = (1/3) * root(3) / 5 perhaps
2014-10-12T10:32:37+05:30

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Certified answers contain reliable, trustworthy information vouched for by a hand-picked team of experts. Brainly has millions of high quality answers, all of them carefully moderated by our most trusted community members, but certified answers are the finest of the finest.
 f_{k}  =  μN

So we have N = mgcos30

 f_{k}  =  μmgcos30

now the 
s = ut + 1/2at²
8 = 1/2a . 4
a = 4 m/s²

so now we get a equation for external forces

ma + μmgcos30 = mgsin30

cancelling m

a + μgcos30 = gsin30
μ = (gsin30 - a)/gcos30
μ = (5 - 4)/5√3    (g = 10 m/s²)
μ = 1/5√3
μ = 0.1154 

0
plz mark as best
but answer is 3*square root of3/5
it was given in text book
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