What will be the weight of a box, mass 10Kg on the surface of a hypothetical planet having mass double of Earth and the radius is 3 times of Earth

           W ’= 21.78 kg

Explanation:

The expression for weight is

          W = m g

let's look for the acceleration of gravity with the universal law of gravitation

          F = G m M / r2

          F = m (G M / r2)

without comparing the two equations

          g’= G M / r2

in that case M = 2 Mo and r = 3 ro

where mo and ro are the mass and radius of the earth

         we substitute

         g ’= G 2Mo / (3r₀) 2

         G ’= 2/9 G Mo / r₀²

         g ’= 2/9 g

the weight of the body on this planet is

         W ’= m g’

          W ’= m 2/9 g

let's calculate

          W ’= 2/9 10 9.8

           W ’= 21.78 kg

its c its is a mixture of gases

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.

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.

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 . this process does not change the mass number.

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 -decay. in this the mass number remains same.

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