Physics, asked by shrijha15shrijha, 1 year ago

1.when a person jumps out of a boat, it moves backward why?
2.calculate the change in momentum of a body weighing 5kg when its velocity decreases from 20m\s to 0.2m\s
3. a heavy and light object have the same momentum. which of these is traveling fast?
4. if action is always equal and opposite to reaction, why don't the two cancel each other?

Answers

Answered by Dhinu
0
1. when a person jumps out of a boat , it(boat) moves backward .. bcoz
practically:- the guy pushes the boat to jump to a side so, the boat moves to the side opposite to where the person jumps ......
scientifically:- the momentum of system is conserved.... so, if guy jumps to a side , boat will move to another side (negative of velocity to the velocity of guy )

2. change in momentum = m ( v2 - v1) { v2 = final velocity and , v1 = initial velocity}
=> change in momentum = 5 (0.2 - 20)
=> change in momentum = 5 x(- 19.8) = (-99) kg-m/s ....

3. A heavy and a light object have the same momentum then, the lighter one is traveling fast ....
let m1 = mass of heavy object ,V1 = velocity of heavy object , m2 = mass of lighter object and , V2 = velocity of lighter object ....
their momentum is same ...
So, m1v1 = m2v2
=> (m1/m2) = (V2/V1) -----(1)
and.. m1 > m2 (m1 is heavier than m2)
so, V2 > V1 (for the equation (1) to be corrected) ..
hence , the velocity of lighter particle is high ...
=> the lighter particle travels fast ...

4. Action is always equal and opposite to reaction ...
let's consider a situation when you punch a wall ...
the Action is that you are punching the wall
that means you are applying force on the wall ...
and the reaction is that the wall is forcing you (your hand) ..
So, the action and reaction applies on different objects .. (not on the same object) so.. the forces will not cancel each other ... (they would cancel if both the forces applies on the same object) .... it's just .. both forces (action and reaction) are equal and opposite in direction and... the both are applied on different object ...
Another example:- If A put a action force on B.. then B will put a reaction force on A ... so, action force is applied by A on B .. and reaction force is applied by B on A....
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