The RRB Group D Results are expected to be out soon! The Railway Recruitment Board released the RRB Group D Answer Key on 14th October 2022. The candidates will be able to raise objections from 15th to 19th October 2022. The exam was conducted from 17th August to 11th October 2022. The RRB (Railway Recruitment Board) is conducting the RRB Group D exam to recruit various posts of Track Maintainer, Helper/Assistant in various technical departments like Electrical, Mechanical, S&T, etc. The selection process for these posts includes 4 phases- Computer Based Test Physical Efficiency Test, Document Verification, and Medical Test.
As @SchrodingersCat explained, there will be no work on the system if the force is orthogonal to the displacement. However, I would like to elaborate the answer a little further.
An object can move even without a force (Newton's first law says about this), the motion however will be an unaccelerated one. So a body could displace even if there is no force. If you have studied classical mechanics, you may have heard that it is the linear momentum which is the generator of translation, not force.
In Euclidean geometry, orthogonal vectors implies mutually perpendicular vectors. However, the actual sense is that the two vectors are independent. This means that one has no common component with the other, which according to the above discussions states that one vector has no effect on the other. So, the displacement occurred is not due to the force given. Geometrically, that is possible only if force and displacement are perpendicular so that their dot product vanishes. This is why there is no work done on the system if the applied force and the resultant displacement are perpendicular. But, that perpendicular force could affect the direction of motion of the body (since a force on a body should accelerate it somehow). So, no work is needed to change the direction of a body, even though it happens only by a force. In such a case, there is no displacement due to the force applied, only a change in direction- the effect of which is defined by the torque on the body (the rotational analogue of force). [1]: "effect" in the present context is used to imply anything that can contribute to work. We cannot say that the force has no effect on the object. It could accelerate the body, even if no displacement has happened due to that force, which is by changing the direction of motion. |