#### (a) Calculate the height of a cliff if it takes 2.35 s for a rock to hit the ground when it is thrown straight up from the cliff with an initial velocity of 8.00 m/s.

(b) How long would it take to reach the ground if it is thrown straight down with the same speed?

**SOLUTION:**

Part a

Refer to Figure 2.47a.

The known values are:

Based from the given values, we can use the equation . Substituting the values, we have

Therefore, the cliff is 8.26 meters high.

Part b

Refer to Figure 2.47b.

The knowns now are:

Based from the given values, we can use the equation . Substituting the values, we have

Using the quadratic formula to solve for the value of t, we have

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