If you drop your Keys, their momentum increases as they fall. Why is the momentum of the Keys not conserved? Does this mean that the momentum of the universe increases as the keys fall? Explain.
Answer to Problem 1CQ
Explanation of Solution
The rate of change in momentum is called force. When the key is dropped, there are a number of forces act on the key. The first force is the weight of the key that act downwards and the other force is the gravitational force that is act between the two bodies that are the Earth and the key.
Since the mass of earth is very large compare to the mass of key. So, the attractive force tends to attract the key more strongly than the key to the earth and there is downward force that support the downward force which concludes the net momentum act on the key is in downward direction and increases due to acceleration of the key is increases so the momentum of the key is not conserved.
The momentum of the universe is conserved as the universe consists of planets and stars in which the planets move around the sun in a fixed orbit because of the equal and opposite force that makes them to move in a fixed orbit. The net amount of force acting by the universe on the earth is equal and opposite that makes the momentum of the universe conserved.
Conclusion
Therefore, the momentum of the key is not conserved as the forces acting on the key are not balanced and the momentum of the universe is conserved.
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