Physics
In the gamma decay of a nucleus

Both the mass number and the atomic number of the nucleus change
The mass number of the nucleus does not change whereas its atomic number changes
The mass number of the nucleus changes whereas its atomic number does not change
Neither the mass number nor the atomic number of the nucleus changes

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Physics
A metal ball and a rubber ball, both having the same mass, strike a wall normally with the same velocity. The rubber ball rebounds and the metal ball does not rebound. It can be concluded that

The initial momentum of the rubber ball is greater than that of the metal ball
Both suffer the same change in momentum
The rubber ball suffers greater change in momentum
The metal ball suffers greater change in momentum

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