Question

A body is allowed to slide down on a smooth inclined plane. For a given base length, the time taken by the body to reach the bottom will be minimum if the angle of the inclined plane is:

• A. ${30}^0$
• B. ${45}^0$
• C. ${60}^0$
• D. ${75}^0$

Answer 1

Answer: (D)

${75}^0$

The force acting on the body along the plane is $mgsin\theta$ and hence the acceleration will be $gsin\theta$
since, s=$\frac{1}{2}a{t}^2$
more the acceleration, less the time it will take, and here acceleration is greater here for greater angle. (between 0 and 90 degrees.)