A pendulum made of a string of length 11.6 m and a spherical bob of mass 2.8 kg is
able to swing in a vertical plane. The pen-
dulum is released from an angular position
38° from vertical as shown in the figure be-
low. The string hits a peg located a distance
5 m below the point of suspension and swings
about the peg up to an angle a on the other
side of the peg. Then, the bob proceeds to
oscillate back and forth between these two
angular extremities.
The acceleration of gravity is 9.8 m/s?.

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.