Can a Man Catch a Constantly Accelerating Train?

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A train accelerates from rest with a constant acceleration 'a', while a man chases it from a distance 'b' at a constant speed 'V'. The condition for the man to catch the train is established as V² > 2ab. This inequality arises from the quadratic equation formed when equating the distance traveled by both the train and the man. The discussion emphasizes the necessity of ensuring that the quadratic equation has a physically meaningful solution, which is critical for determining the catch-up time.

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Jess1986
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:confused: Please help with this problem. A train moves from rest with const accel. a in a straight line. A man at distance b behind the train chases it with const. speed V. Show he can catch it if V^2 >2ab, and find when he does so.
I have found formulas for distance traveled for each and equated these but cannot understand where the Vsquared comes from.
Thanks to anyone who can help. Jess x
 
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Hint: When you equate those distance formulas you'll get a quadratic equation. What must be true for that quadratic to have a physically meaningful solution?
 

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