Question

how much height should the obstacle so that ball will be in equilibrium

Answer 1

An easy way to solve this Multiple Choice Question is just by trial and error. As we can know for a fact that if theta=0" role="presentation" style="margin: 0px; padding: 0px; outline: 0px; display: inline; font-style: normal; font-weight: normal; line-height: normal; font-size: 14px; text-indent: 0px; text-align: left; text-transform: none; letter-spacing: normal; word-spacing: normal; word-wrap: normal; white-space: nowrap; float: none; direction: ltr; max-width: none; max-height: none; min-width: 0px; min-height: 0px; border: 0px; position: relative;">theta=0theta=0 then h should be equal to zero. So by substituting the theta value as zero in the options given to find out the satisfying equation, which turns out to be option D.