Editor Staff asked 1 year ago
A disc is purely rolling down an inclined plane of length ‘l’ & angle θ. What is the value of friction acting on it? Let the mass of the disc be M & radius be R.
(a) (Mgsinθ)/3
(b) 0
(c) (4Mgsinθ)/3
(d) (2Mgsinθ)/3
I have been asked this question in homework.
This interesting question is from Rolling Motion topic in portion System of Particles and Rotational Motion of Physics – Class 11
Select the correct answer from above options
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Editor Staff answered 1 year ago
The correct option is (a) (Mgsinθ)/3
To elaborate: Let the angular acceleration of the disc be ‘α’. And the linear acceleration along the incline be ‘a’. For pure rolling, a = Rα. Mgsinθ – f = Ma———-(1), where f is the friction.
fR = Iα————–(2), where I is the moment of inertia = MR^2/2.
fR = Ia/R, we substitute the value of a into the first equation,
Mgsinθ – f = (MfR^2)/( MR^2/2) = 2f
∴ Mgsinθ – f = 2f Or f = (Mgsinθ)/3.
