A man driving a car traveling at 20 m/sec slams on the brakes and decelerates at 3.25 m/s^2. How far does the car travel before it stops?

Recall that

where and are initial and final velocities, respectively; is acceleration; and is the net displacement, or distance if the object is moving in a single direction.

The car has initial speed 20 m/s and acceleration -3.25 m/s². It comes to a stop, so it has 0 final speed. Then

0² - (20 m/s)² = 2 (-3.25 m/s²) ∆x

∆x = (20 m/s)² / (7.5 m/s²) ≈ 53.3 m

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.