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 deceleration, 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 deceleration, calculate the number of revolutions made by it before coming to rest.
Answer» SOLUTION :Here, `omega_(0)=120` r.p.m `=2` r.p.s `=4pirads^(-1)` `omega=0` and `t=10s` `omega=omega_(0)+at` `0=4pi+axx10` or `a=-0.4pirads^(-2)` Also, the angle covered by the motor, `theta=omega_(0)t+(1)/(2)at^(2)` `:. theta=4pixx10+(1)/(2)xx(-0.4pi)xx10^(2)=40pi-20PI` `=20pi`rad Hence, the number of revoluations COMPLETED `n=(theta)/(2pi)=(20pi)/(2pi)=10`