Explanation:
Equation for energy balance will be as follows.


Hence, 
Therefore, we will calculate the final temperature as follows.

= 868.03 R
Now, we will calculate the mass as follows.
m = 
= 
= 1.031 lbm
Hence,

Putting the values into the above equation as follows.


= 655.2 Btu
Thus, we can conclude that work done by paddle wheel is 655.2 Btu.
Momentum is conserved in a collision. Momentum is mass*velocity, so you can find your answer by calculating initial and final momentums and setting them equal to each other.
15kg * 3.50 m/s + 9kg * 2.35 m/s = 73.65 kg m/s
73.65 = 9 * 2.8 + 15x
solve for x
x= 3.23
The final velocity is 3.23 m/s
Newton's first law of motion - sometimes referred to as the law of inertia. Newton's first law of motion is often stated as. An object at rest stays at rest and an object in motion stays in motion with the same speed and in the same direction unless acted upon by an unbalanced force.
I’m pretty sure the answer is 3