The dominant form of drag experienced by vehicles (bikes, cars, planes, etc.) at operating speeds is called form drag. it increases quadratically with velocity (essentially because the amount of air you run into increases with v and so does the amount of force you must exert on each small volume of air). thus fdrag = c dav2, where a is the cross-sectional area of the vehicle and cd is called the coefficient of drag.

consider a vehicle moving with constant velocity v. find the power dissipated by form drag.

To solve this problem it is necessary to resort to the concepts related to energy, power, speed and force.

By definition we know that Power is the Amount of Energy used over a period of time, that is

Energy in turn is the amount of force used during a given distance, that is

Replacing at the first equation we have that

For the kinematic equations of movement description we have that velocity is equivalent to

Then,

Here the force is equal to the drag force, then

Since  are opposite therefore cos180=-1

Where,

Drag coefficient

A = Area

V = Velocity

Finally we have the expression:

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.

mistakes are ok