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nikhil arora Grade: 12
        

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7 years ago

Answers : (3)

vikas askiitian expert
510 Points
										

total change in height = dh =H-R =50cm=0.5m

from work energy theorem,

 change in kinetic energy = total work

  kinetic energy = mgdh

 mv2(1+k2/r2)/2 = mgh

 mv2= 2mgh/(1+k2/r2)    .....................1

k is radius og gyration & for sherical ball it is Rsqrt(2/5) ...

mv2 = 10mg/7           .................2

now when theta =0 then

   N  = mv2/R

so N = 10mg/7R=10Newton

since the body is not falling off so net friction force should be equal to weight =mg

f = 0.7newton

7 years ago
nikhil arora
54 Points
										

thanks for the reply.... normal reaction is correct but frictional force is wrong by ur answer..... the right answer is 0.2 N 

 

sorry ,i forgot to tell that it is small sphere that is is rolling down the inclined plane ....

 

i did it this way (but failed)

frictional force = f , alpha=angular acceletion

at  point A

f - mg = ma..... (1)

f . r = I (alpha)....(2)

putting f = I (alpha)/r in (1)

I(alpha)/r=m(g+a)

for sphere I=2mr(square)/5 and alpha=a/r

so

2mr(sqr)/5 * a/r * 1/r=m(g+a)

2/5 a= g+a

a=-5/3g

putting this in (1)

i got f=0.46

 

plz remove my confusion

thanks

7 years ago
vikas askiitian expert
510 Points
										

 eq 1 should be

   mg - f = ma ..........1

(this is because ,direction of net force on center of mass is downward ...)

  f = Ia/r2

mg = 7f/2

f = 2mg/7 =0.2N ans

please approve if u like my ans

7 years ago
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