Refrigerant entering the compressor of a refrigeration system is sub-cooled liquid
The liquid refrigerant is sub-cooled to ensure that only liquid and not the vapour enters the throttling valve. In a refrigeration system, the superheating decreases COP increase refrigerating effect but increasing amount of work done. The coefficient of performance or COP (sometimes CP or CoP) of a heat pump, refrigerator or air conditioning system is a ratio of useful heating or cooling provided to work (energy) required. Higher COPs equate to higher efficiency, lower energy (power) consumption and thus lower operating costs.
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Answer:
The value of impulse of the net force on the ball during its collision with wall is 
The value of average horizontal force that the wall exerts on the ball during the impact is F = 15000 N
Explanation:
Mass of the ball = 0.5 kg
Horizontal velocity
= 20 
Velocity after collision
= - 10 
(A). Impulse of the net force on the ball during its collision with wall is

I = 0.5 × (20 + 10)

This is the value of impulse of the net force on the ball during its collision with wall.
(B). The magnitude of average horizontal force

Where F = Force
I = impulse & t = time interval = 0.001 sec

F = 15000 N
This is the value of average horizontal force that the wall exerts on the ball during the impact.
A textbook but if there none to good use try google
To determine the velocity in the restriction, we need to remember the law of conservation of mass where mass in should be equal to the mass out since mass cannot be created or destroyed. For this system, mass flow rate in is equal to mass flow rate out. We do as follows:
Mass flow rate in = Mass flow rate out
density (volumetric flow rate in) = density (volumetric flow rate out)
Since the liquid in and out are the same, then density would be cancelled.
(volumetric flow rate in) = (volumetric flow rate out)
Area in x velocity in = Area out x velocity out
velocity out = area in x velocity in / area out
velocity out = π (4/2)^2 (1.0) / π (2/2)^2
velocity out = 4 m/s