A railroad car, with a mass of 25,000 kg, is moving north along a track at 4.5 m/s. It has a collision with another railroad car that is full of coal and therefore has a much larger mass of 58,000 kg. The two railroad
cars “couple” and move as one unit after the collision. What is the final velocity of the two railroad cars?
Assume the second car was initially at rest. (Round your answer to the nearest tenth.)

V = 1.35 m/s

Explanation:

Given that,

Mass of a railroad car, m₁ = 25,000 kg

Initial speed of a railroad car, u₁ = 4.5 m/s

Initial speed of railroad car that is full of coal, u₂ = 0 (at rest)

We need to find the final velocity of the two railroad cars if they move as one after the collision. It is a case of inelastic collision in which the momentum remains conserved. Using the conservation of linear momentum as follows :

V is the final speed and u₂ = 0

So, the final velocity of the two railroad cars is 1.35 m/s.

Molecular mass of ethylene glycol is 62 g/mol and molality of solution will be 9.39 mol/kg.

Explanation:

To calculate the molar mass of ethylene glycol, we add the mass of each element multiplied with their individual atoms.

Mass of oxygen atom = 16 g/mol

Mass of hydrogen atom = 1 g/mol

Mass of carbon atom = 12 g/mol

Mass of ethylene glycol =

Molality of the solution is defined as the ratio of moles of solute to the mass of solvent present in kilograms.

Mathematically,

Water is the solute and ethylene glycol is the solvent in this case.

We are given:

Mass of solute (water) = 1.2 kg = 1200 g      (Conversion factor: 1 kg = 1000 g)

Molar mass of solute (water) = 18 g/mol

Mass of solvent (ethylene glycol) = 7.1 kg

Putting values in above equation, we get:

Hence, molecular mass of ethylene glycol is 62 g/mol and molality of solution will be 9.39 mol/kg.