Two students analysed two different problems off mechanics involving constraint motion. Symbols have their usual meaning.

The vertical rod can move only vertically and the wedge can move only horizontally.
`y/x=tantheta, y=x tan theta, v_(y)=v_(x)tantheta`
Student `B`.
The ends of the rods are slipping on the ground and the wall, respectively
`y/x=tantheta, y=xtantheta, vy=vxtantheta`

Options

A. Student `A` is correct `B` is wrong
B. Student `A` is wrong `B` is correct
C. Both are correct
D. Both are wrong

Answer

A

Explanation

Displacement along the common normal will be the same.
`ycostheta=xsinthetaimpliesy=xtantheta`. Differentiating both sides, `vy =vxtantheta`.
Velocity of the two ends of the rod will be the same along the rod.
`vysintheta=vxcostheta`
`implies vy=vxcottheta`
Student `A` is correct and `B` is wrong.