A ball, dropped from rest, covers 2/7 of the distance to the ground in the last two seconds of its fall.(adsbygoogle = window.adsbygoogle || []).push({});

(a) From what height was the ball dropped?

(b) What was the total time of fall?

If I can figure out either part a or part b, the other part will be easy.

I have a feeling that the solution to this will involve simultaneous equations. But I don't really know where to begin aside from making a list of everything I know:

[tex]d_{t} = d_{1} + d_{2}[/tex]

[tex]d_{t} = \frac {2}{7} d + \frac {5}{7} d[/tex]

[tex]t_{t} = t_{1} + t_{2} [/tex]

[tex]t_{t} = t_{1} + 2 seconds[/tex]

[tex]v_{i_{t}} = 0[/tex]

[tex]v_{f_{t}} = v_{f_{2}}[/tex]

[tex]d_{1} = \frac{5}{7}d_{t}[/tex]

[tex]t_{1} = t_{t} - t_{2}[/tex]

[tex]t_{1} = t_{t} - 2 seconds[/tex]

[tex]v_{i_{1}} = 0[/tex]

[tex]v_{f_{1}} = v_{i_{2}}[/tex]

[tex]d_{2} = \frac{2}{7} d_{t}[/tex]

[tex]t_{2} = 2 seconds[/tex]

[tex]v_{i_{2}} = v_{f_{1}}[/tex]

[tex]v_{f_{2}} = v_{f_{t}}[/tex]

Can anyone suggest a starting point?

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# Homework Help: Kinmatics problem

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