If a rock is thrown upward on the planet Mercury with a velocity of $30\text{m/s,}$ its height after $t$ seconds is given by the equation $h(t) = 30 t-1.8 t^2.$

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1. Find the velocity of the rock after one second.
Velocity (in m/s):

2. Find the velocity of the rock when $t = a.$
Velocity (in m/s): $v(a) =$

3. When will the rock hit the surface?
Time (in sec): $t =$

4. With what velocity will the rock hit the surface?
Velocity (in m/s):

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