MCQ
How long will a train, running at a speed of $45\ kmph$ cross a standing man, given the length of the train is $450\ m\ ?$
- A$100\ sec$
- B$150\ sec$
- C$50\ sec$
- ✓$36\ sec$
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$\vec r = - \cos \,t\hat i + \sin \,t\hat j - 18\,t\hat k$
then what is the magnitude of its acceleration ?