Dear Aman, the PWD certificate is provided to those candidates who fall under the guidelines set under Disability Act after being examined by a Medical Professional. Now the IIT authorities dont know you up and personal to consider your statements true without proper proof. It's just not you alone but there will be quite a few students who apply under this category. To ensure that the reservation and privileges are not being misued and the truly desrved candidates are not robbed off an opportunity, IIT authorities conduct test on every individual. If your case is genuine and honest and the disability mentioned and certificate granted hold true to the range of disability, you needn't be worried about the physical examination.