To tackle this problem, it's essential to employ concepts associated with force as per Hooke's law, alongside the forces described by Newton's second law and the concept of potential elastic energy. Since the forces are in equilibrium, the spring force matches the gravitational force. To find the spring constant k, we recognize the compression is 40cm at launch, hence applying the potential elastic energy formula results in determining the energy stored in the spring as 63.72 Joules.
First, we must transform the pressure into SI units, considering that

:

The starting and ending volumes of the gas will be as follows (keeping in mind that

):


Thus, the work performed on the gas by its surroundings is

The positive outcome indicates that this work leads to a rise in the gas's internal energy.
Response:
0.60 m/s
Details:
The average speed between times t = a and t = b can be expressed as:
v_avg = (x(b) − x(a)) / (b − a)
Given the function x(t) = 0.36t² − 1.20t, and considering the interval from 1.0 to 4.0:
v_avg = (x(4.0) − x(1.0)) / (4.0 − 1.0)
v_avg = [(0.36(4.0)² − 1.20(4.0)) − (0.36(1.0)² − 1.20(1.0))] / 3.0
v_avg = [(5.76 − 4.8) − (0.36 − 1.20)] / 3.0
v_avg = [0.96 − (-0.84)] / 3.0
v_avg = 0.60
The average speed calculated is 0.60 m/s.