Answer:
Because of the presence of air resistance
Explanation:
When an object is in free fall, ideally there is only one force acting on it:
- The force of gravity, W = mg, that pushes the object downward (m= mass of the object, g = acceleration of gravity)
However, this is true only in absence of air (so, in a vacuum). When air is present, it exerts a frictional force on the object (called air resistance) with upward direction (opposite to the motion of free fall) and whose magnitude is proportional to the speed of the object.
Therefore, it turns out that as the object falls, its speed increases, and therefore the air resistance acting against it increases too; as a result, the at some point the air resistance becomes equal (in magnitude) to the force of gravity: when this happens, the net acceleration of the object becomes zero, and so the speed of the object does not increase anymore. This speed reached by the object is called terminal velocity.
Answer:
The change in momentum is 
Explanation:
From the question we are told that
The time taken for the stone to stop is 
The net force on the rock is 
The impulse of the rock can be mathematically represented as

Substituting values


Now impulse is defined as the rate at which momentum change
Hence the change in momentum
of the rock is equal to the impulse of the rock
So

Whats the question?
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Answer:

Explanation:
We are given that three resistors R1, R2 and R3 are connected in series.
Let
Potential difference across 
Potential difference across 
Potential difference across 
We know that in series combination
Potential difference ,
Using the formula

Hence, this is required expression for potential difference.