A baseball is traveling (+30m/s) and is hit by a bat. It leaves the bat traveling (−40m/s). What is the change in its velocity? Unlike some others, this is any choice, so not just 4 choices!

Explanation:

The change must be 30 - - 40 which means it came in a 30 meters / second and went out in the opposite direction at 40 meters / second

The change is 70 m/sec.

You could show it to be - 70 meters per second as well. That's done by making the outgoing direction minus.

Delta v = vf - vi.

Now it depends on which way you define vf and vi.

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.