Ez the answer to your question would be
(-4) cecause I am super smart ? 931
Answer:
a. -5,4
b. 28
Explanation:
(see how to solve in pic)
Answer:

Explanation:
Using the conservation of energy we have:

Let's solve it for v:

So the speed at the lowest point is 
Now, using the conservation of momentum we have:

Therefore the speed of the block after the collision is 
I hope it helps you!
Send wave from your location to the object and wait until echo is back.
Measure the time taken.
If you know the speed of wave (say sound wave), than just multiply by half time taken wave to return