1. Calculate the forc e required to take away a flat circular plate of radius 0.01m from the surface of the water. The surface tension of water is 0.075 N/m.

r=0.01m

t=0.075n/m

f?

d=2πr

d=2×3.14×0.01

d=0.0628

T=0.075n/m

f=T×d

f= 0.075×0.0628

f=0.00471

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.

seeing the graph would