A train.s average speed is 72 km/h but is reduced to 60 km/h due to stoppages. For how much time does the train stop in an hour?
एक ट्रेन की औसत चाल 72 किमी/घंटा है लेकिन रुकने के कारण यह कम हो कर 60 किमी/घंटा रह जाती है | एक घंटे में ट्रेन कितने समय के लिए रूकती है ?

Options

A. 2min
B. 4min
C. 5min
D. 6min

Answer

A

Explanation

`omega_(0)= 2pi xx (330)/(60)= 11pi` rad/sec
`omega= 2pi xx (110)/(60)= (11pi)/(3)` rad/s
`alpha= ((11pi)/(3)- 11pi)/(2 xx 60) = (-22pi)/(3 xx 2 xx 60)= (-11pi)/(180)` rad/s
`omega= omega_(0) + alpha t_(1) rArr t_(1)= 120= 2` min