A body moves in a circle at constant speed. Does the centripetal force that accelerates the body do any work? Explain.

If a body moves in a circular path then centripetal force that accelerates the body does not do any work

Explanation:

Reason 1:

As we know that work done on a body is equal to the force applied multiplied by the displacement covered i.e. W=Force.displacement

When a body is moving in a circular path it means it is coming back to the starting point so its displacement is zero thus work done by a body moving in a circular path with a constant speed is zero.

i.e. Work-done=force.0

W=0  

Reason 2:

As we know that work done on a body is equal to the force applied multiplied by the displacement covered in the direction of force applied but if the force is inclined at an angle then work done on a body is equal to the product of the component of force in the direction of displacement and its displacement.

W=F.S cosθ

As the force on the body is centripetal force which is always directed towards the center of the circle (i.e. acting along the radius of the circle) which is  at right angle to the direction of the displacement (i.e. the direction of the displacement is always tangential to the circle)

i.e. θ=90°

W=F.S cos90°

W=F.S×0

W=0

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.