To solve this problem it is necessary to apply the kinematic equations of motion and Hook's law.
By Hook's law we know that force is defined as,

Where,
k = spring constant
x = Displacement change
PART A) For the case of the spring constant we can use the above equation and clear k so that




Therefore the spring constant for each one is 11876.92/2 = 5933.46N/m
PART B) In the case of speed we can obtain it through the period, which is given by

Re-arrange to find \omega,



Then through angular kinematic equations where angular velocity is given as a function of mass and spring constant we have to




Therefore the mass of the trailer is 4093.55Kg
PART C) The frequency by definition is inversely to the period therefore



Therefore the frequency of the oscillation is 0.4672 Hz
PART D) The time it takes to make the route 10 times would be 10 times the period, that is



Therefore the total time it takes for the trailer to bounce up and down 10 times is 21.4s
100N describes the weight of the sandbag, while 100kg is the mass of the sandbag.
To calculate acceleration, divide your weight by the mass, thus the accleration is:
D is the wrong answer. New information does often completely change the theory. Its hard to change something and leave the major theory intact.
The gas is in a rigid container: this means that its volume remains constant. Therefore, we can use Gay-Lussac law, which states that for a gas at constant volume, the pressure is directly proportional to the temperature. The law can be written as follows:

Where P1=5 atm is the initial pressure, T1=254.5 K is the initial temperature, P2 is the new pressure and T2=101.8 K is the new temperature. Re-arranging the equation and using the data of the problem, we can find P2:

So, the new pressure is 2 atm.