Suppose a ball of mass 'm' is thrown vertically upwards with an initial speed 'v',its speed decreases continuously till it becomes zero. Therefore the ball begins to fall downward and attains the speed 'v' again before striking the ground. It implies that the magnitude of initial and final momenta of the ball are same. Yet,it is not an example of conservation of momentum. Explain why??
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☆ momentum conservation:-
- it implies that if there is no external force is applied to the system then its initial state of motion or rest will be equal to final state of motion or rest
- means P(initial)=P(final)
- now momentum is a vector ..so its remains constant means both magnitude and direction remain constant...
- internal forces which act on the system does not change the momentum...
☆now to your ques •••
- the force which is only acting throughout is gravitational force...
- gravitational force is type of non contact force which applied by earth by creating a field strength which attracts everything
- so as the during the process a external force (gravity) which is responsible for changing the P of the ball ....that is why it came down...OTHERWISE it will forever go upwards....isn't it??
- so yes ,a ext force present no momentum is conserved
Yes, but you can say that energy is conserved here...bcz it go up with some KE which gets into PE at highest then again convert to KE....
ignoring the air resistance....if its considered then it will not have v same velocity during coming downward.
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