JEE Main2017PhysicsLaws of MotionActual
The machine as shown has 2 rods of length 1 m connected by a pivot at the top. The end of one rod is connected to the floor by a stationary pivot and the end of the other rod has roller that rolls along the floor in a slot. As the roller goes back and forth, a 2 kg weight moves up and down. If the roller is moving towards right at a constant speed, the weight moves up with a :
Options
- ASpeed which is 3 4 t h of that of the roller when the weight is 0 . 4   m above the ground
- BConstant speed
- CDecreasing speed
- DIncreasing speed
Correct answer
C. Decreasing speed
Step-by-step solution
v A = d x d t = d 2 l cos θ d t = - 2 l sin θ d θ d t and Vertical velocity of B , v B = d y d t = d l sin θ d t = l cos θ d θ d t v A v B = - 2 tan θ ⇒ v B = - v A cot θ 2 θ → increase cot θ → decrease Hence, v B → decrease.