JEE Main Solved Question 2020 Physics

 Question 4 : A uniform cylinder of mass 'M' and radius 'R' is to be pulled over a step of height 'a' (a<R) by a force 'F'at it's centre 'O' perpendicular to the plane through the axis of the cylinder on the edge of the step  as shown in figure. The minimum value of 'F' required is


Answer: Apply the principle of moment about the edge of the step C

Sum of clockwise moment=Sum of anticlockwise moment

Just before rolling

`F× R=Mg×d`---------------(1) (where d=CB from figure)

Applying Pythagores theorem in 𝚫OBC

`R^2=(R-a)^2+d^2`

`d=sqrt(R^2-(R-a)^2)`

substitute for d in (1)

`F=(Mg/R)×R×sqrt(1-((R-a)/R)^2)`

`F=Mg×sqrt(1-((R-a)/R)^2)`

Watch Video with explanation 

 

 

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