It will be unstable system because it will not be able to recover from the disturbance
Answer:
Moment of the force is 20 N-m.
Explanation:
Given:
Force exerted by the person is, 
Distance of application of force from the point about which moment is needed is, 
Now, we know that, moment of a force 'F' about a point at a perpendicular distance of 'd' from the same point is given as the product of the force and the perpendicular distance.
Therefore, the moment of the force about the end of the claw hammer is given as:

Hence, the moment of the force exerted by the person about the end of the claw hammer is 20 N-m.
Answer:
The Internal energy of the gas did not change
Explanation:
In this situation the Internal energy of the gas did not change and this is because according the the first law of thermodynamics
Δ U = Q - W ------ ( 1 )
Δ U = change in internal energy
Q = heat added
W = work done
since Q = W. the value of ΔU will be = zero i.e. No change
If they both are moving with the same speed and direction
i.e. covering the same distance in the same time interval in the same direction