A student is late and running to class. A hall monitor tells them to slow down, so the student slows to a walking speed of 1.4 m/s. It takes the student 3.0 seconds to slow to this speed, due to the student’s -2.5 m/s2 acceleration. What was the student’s initial speed

8.9m/s

Explanation:

Final velocity = initial velocity + acceleration *time

Vf=vi+at

Vf=1.4 m/s

Vi=?

A=-2.5m/s^2

T=3

1.4m/s=vi+(-2.5m/s^2)(3s)

Vi=8.9m/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.