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Standing at the top of a 30.0 m high cliff, you throw a rock straight down with a velocity of 8.00 m/s. After how many seconds does it hit the ground?

Respuesta :

Answer:

It will take 1.789 sec  

Explanation:

We have given height h = 30 m

Initial velocity u = 8 m/SEC

Acceleration due to gravity [tex]g=9.8m/sec^2[/tex]

Now according to second equation of motion [tex]h=ut+\frac{1}{2}gt^2[/tex][tex]30=8t+4.9t^2[/tex]

[tex]4.9t^2+8t-30=0[/tex]

After solving we get t = -3.42 sec and t = 1.789 sec

As negative time is not possible so time will be 1.789 sec

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