The chart describes four objects experiencing one or more frictional forces. Which statement explains the type of friction acting on each object? a. The bike has rolling friction, the sled and the motorcycle have sliding friction, and the elephant has static friction.

b. The bike and sled have sliding friction, and the motorcycle and elephant have static friction.

c. The bike has static friction, the sled and elephant have sliding friction, and the motorcycle has rolling friction.

d. The bike and motorcycle have rolling friction, the sled has static friction, and the elephant has sliding friction.

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.