Physics, 23.01.2020 21:31 mpatel12

Which of these is always conserved in a collision in a closed system?

a) momentum and energy
b) momentum and mechanical energy
c) energy only
d) momentum and kinetic energy

Answers: 2

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Answer from: caitlyn73

B) momentum and mechanical energy

Explanation:

In classical physics, a closed system is a system that does not exchange any matter with the surrounding, and on which there are no external forces acting on it.

Due to this definition, we have the following consequences:

- In a collision in a closed system, momentum is always conserved. This is because there is exchange of matter with the surroundings (so, no mass can be lost), and also because there are no external forces acting on the objects inside the system. In fact, the variation of the total momentum of the system is related to the net force acting on the system:

$F=\frac{\Delta p}{\Delta t}$

but since the net force F is zero, then the variation of momentum, $\frac{\Delta p}{\Delta t}$ , is also zero, therefore the momentum is constant.

- Also, mechanical energy is conserved. Mechanical energy is the sum of potential energy and kinetic energy of the system: again, since there are no external forces acting on the system, energy cannot be dissipated, so the total energy of the system cannot change.

Answer from: Quest

answer: the correct answer is 1.

explanation: there are various process in which a radioactive nuclei decays:

1) alpha decay: in this process, a heavier nuclei decays into lighter nuclei by releasing alpha particle. the mass number is reduced by 4 units.

$_a^z\textrm{x}\rightarrow _{a-2}^{z-4}+_2^4\alpha$

2) electron capture: in this decay process, a parent nuclei absorbs an electron and gets converted into a neutron. simply, a proton and an electron combines together to form a neutron. mass number does not change in this process.

$_a^z\textrm{x}+_{-1}^0\textrm{e}\rightarrow _{z-1}^a\textrm{y}$

3) gamma ray emission: it is a decay process in which an unstable nuclei gives excess energy by a spontaneous electromagnetic process. this decay releases $\gamma -radiations$ . this process does not change the mass number.

$_a^z\textrm{x}^*\rightarrow _a^z\textrm{x}+_0^0\gamma$

4) positron emission: it is a type of decay process, in which a proton gets converted to neutron and an electron neutrino. this is also known as $\beta ^+$ -decay. in this the mass number remains same.

$_a^z\textrm{x}\rightarrow _{z-1}^a\textrm{y}+_{+1}^0e$

from the above information, we see that only alpha-decay is producing a change in the mass number of the nucleus.

Answer from: Quest

explanation:

considering the bohr theory, the type of connection that requires the transfer the answer conuldn't be right

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Which of these is always conserved in a collision in a closed system?

a) momentum and e...

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