2. What is
the speed of a ball that is attached to a string and swings in a horizontal
circle of a radius 3.0 m with a centripetal acceleration of 15 m/s2?

Radius = 3 m

Centripetal acceleration = 15 m/s^2

We know, centripetal acceleration= square of Velocity/Radius

or, Square of velocity = Centripetal Acceleration× Radius

Therefore, the square of velocity

= (15 × 3) m/s = 45 m/s

Therefore, the speed

= √45 m/s

= √3×3×5 m/s

= 3√5 m/s

The answer is 3√5 m/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.

it is b. absorbs thermal energy