Decrease because its 0.0 m/s
We know that the change in momentum is equals to the product of force and time that is impulse (
). Therefore, we need to determine the value of that the water is in air by using the second equation of motion,

Here, u is initial velocity which is zero.
.
Thus, impulse

From Newton`s second law,

Therefore, impulse

Given,
and 
Substituting these values, we get
Change in momentum = impulse
.
Answer:
10 :)
You have to divide the difference of speed and divide it by the time. So 100-20 would be 80, and if you divide that by 8 it would be 10.
Hope this helps.
Answer:
The speed of the 11.5kg block after the collision is V≅4.1 m/s
Explanation:
ma= 4.8 kg
va1= 7.3 m/s
va2= - 2.5 m/s
mb= 11.5 kg
vb1= 0 m/s
vb2= ?
vb2= ( ma*va1 - ma*va2) / mb
vb2= 4.09 m/s ≅ 4.1 m/s