A point on the rim of a flywheel has a peripheral speed of 10 `ms^(-1)` at an instant when it is decreasing at the rate of `60ms^(-1)`. If the magnitude of the total acceleration of the point at this instant is `100ms^(-2)`, the radius of the flywheel is

Options

A. `1.25m`
B. `12.5m`
C. `25m`
D. `2.5m`

Answer

A

Explanation

`a_(n)=sqrt(a^(2)-a_(t)^(2))=sqrt((100)^(2)=(60)^(2))=80ms^(-2)`
Now, `a_(n)=(v^(2))/(R)"or"R=(v^(2))/(a_(n))=((10)^(2))/(80)=1.25m`