A boy is sliding down from a third floor window of a building. As he slides down the rope faster and faster, he becomes frightened. Then, he grabs harder on rope, increasing the tension on the rope. As soon as the upward tension in the rope becomes equal to his weight,

Will the boy stop OR will the boy continues down at a constant velocity?

I am convinced that the answer is the 2nd one beacause when a= 0 , the tension force will be equal to weight. Thus when a=0 , velocity will be constant. But the first answ seemed correct as well , because the force will cancel out each other. So how ? Help me


Considering Friction less slide and No Air Resistance

When the tension in the string becomes equal to his weight the boy will stop because if T = mg and the downward force is mgsinϴ and ϴ must be < 90° (slide).

So, According to Second Law, If there is some force there must be some acceleration (in this case retardation).

The Boy will stop sliding.


Every object has inertia, meaning that it wants to continue on the path it is currently on and with the same velocity. That's why, according to the second law, a net force is required to produce acceleration and NOT movement. If an object is travelling at velocity $v$ it will continue to travel at velocity $v$ forever unless a resultant force acts on it.

Therefore, in the example you gave, when the forces balance out the boy just falls at a constant speed, because without a resultant force there is no deceleration slowing him down, and that's because his inertia means he wants to continue moving with a constant velocity.


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