The motor of an engine is rotating about its axis with angular velocity of 120 r.p.m. it comes to rest in 10s, after being switched off. Assuming constant decleration, calculate the number of revolutions made by it before coming to rest.

The motor of an engine is rotating about its axis with angular velocit

1.	The motor of an engine is rotating about its axis with angular velocity of 120 r.p.m. it comes to rest in 10s, after being switched off. Assuming constant decleration, calculate the number of revolutions made by it before coming to rest.
Answer» <html><body><p></p>Solution :Here, `omega_(0)=120 ` r.p.m. = <a href="https://interviewquestions.tuteehub.com/tag/2-283658" style="font-weight:bold;" target="_blank" title="Click to know more about 2">2</a> r.p.s. `= 4pi rad s^(-1)`<br/>`omega = 0`and `t=10 s "" omega = omega_(0)+at`<br/>`0=4pi+axx10` or `a=-0.4 <a href="https://interviewquestions.tuteehub.com/tag/pi-600185" style="font-weight:bold;" target="_blank" title="Click to know more about PI">PI</a> rad s^(-2)`<br/>Also, the angle covered by the <a href="https://interviewquestions.tuteehub.com/tag/motor-1104203" style="font-weight:bold;" target="_blank" title="Click to know more about MOTOR">MOTOR</a>,<br/>`<a href="https://interviewquestions.tuteehub.com/tag/theta-1412757" style="font-weight:bold;" target="_blank" title="Click to know more about THETA">THETA</a> = omega_(0)t+(1)/(2)at^(2)`<br/>`because theta = 4pi xx10+(1)/(2)xx(-0.4 pi)xx10^(2)=40 pi-20pi`<br/>`= 20 pi` rad<br/>Hence, the number of revolutions completed, <br/>`n =(theta)/(<a href="https://interviewquestions.tuteehub.com/tag/2pi-1838601" style="font-weight:bold;" target="_blank" title="Click to know more about 2PI">2PI</a>)=(20pi)/(2pi)=10`</body></html>