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? asked in Education & ReferenceHomework Help · 6 years ago

How do I find time with >only< time given?

These types of problems I'm having issues with.

I need to find time via vertical displacement.

But all I know is that (just for example) vertical displacement is 15 meters.

1 Answer

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  • 6 years ago
    Favorite Answer

    If you mean a free-falling object, then the ideal acceleration is:  g = -9.8 m/sec²

    ... however the initial velocity (Vi) is also needed:

         h = (½) • g • t²  +  (Vi) • t   ...   vertical fall displacement = h

    If the initial velocity (Vi) is zero (or the object is at rest) then:

         h = (½) • g • t²

         t = √ ( 2h ⁄ g )   ...   free-fall time from rest through a vertical displacement = h

         t = √ [ 2(-15) ⁄ (-9.8) ]   ...   time to free-fall 15 m from rest

         t = 1.75 sec

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