Question

An astronaut drops a rock off the edge of a cliff on the Moon.

Answer 1

     Using the Definition fo Average Speed, we have:

$\Delta S (5)=0.8*5^2 \\ \Delta S (10)=20m \\ \\ \Delta S (10)=0.8*10^2 \\ \Delta S (10)=80m \\ \\ \Delta v= \frac{\Delta S (10) - \Delta S (5)}{\Delta t} \\ \Delta v= \frac{80-20 }{10-5} \\ \boxed {\Delta v= 12}$

Number (1)

If you notice any mistake in my english, please let me know, because i am not native.