Answer:
lithium
Explanation:
A lithium atom contains 3 protons in its nucleus irrespective of the number of neutrons or electrons. Notice that because the lithium atom always has 3 protons, the atomic number for lithium is always 3. The mass number, however, is 6 in the isotope with 3 neutrons, and 7 in the isotope with 4 neutrons.
True.
Conductivity is the ability to transmit heat, electricity or sound. Conductivity is a physical property.
A physical property is one which can be measured or observed without changing the composition or identity of a the substance.
Conductivity is a physical property because the composition of the substance does not change.
A copper wire is still a copper wire when it is conducting electricity. Like wise, an aluminum rod is still an aluminum rod when heated. It is conducting heat but the heat does not change it, it is still an aluminum rod during the whole process.
Answer:

Explanation:
Given that
Mass of rifle = M
Initial velocity ,u= 0
Mass of bullet = m
velocity of bullet = v
Lets take final speed of the rifle is V
There is no any external force ,that is why linear momentum of the system will be conserve.
Initial linear momentum = Final linear momentum
M x 0 + m x 0 = M x V + m v
0 = M x V + m v

Negative sign indicates that ,the recoil velocity will be opposite to the direction of bullet velocity.