A piston-cylinder device contains 3 kg of saturated water vapor at 200 kPa. Now heat is transferred to the system at constant pressure until the temperature reaches 200oC. Calculate the work done by the steam during this process.

work done = 117 kJ

Explanation:

given data

mass m = 3 kg

constant pressure P = 200 kPa

temperature T = 200°C

solution

we know that work done by steam is express as

work done = pressure × ΔVolume  1

and here ΔVolume  = final volume - initial volume

we use here steam table and get at pressure 200 kPa

final specific volume = 1.08052 m³/kg

and

initial specific volume = 0.885735 m³/kg

so here

ΔV  = 3 × (1.08052 - 0.885735)

ΔV  = 0.584 m³

so put value in equation 1 we get

work done by steam = 200 × 0.584

work done = 117 kJ

the device is called “ rocket engine”

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.