Which of the following are non-contact forces: friction, electrostatic force, magnetic force, gravity?

Calculate the mass of an object that has a momentum of 100kg x m/sec and velocity of 4 m/sec

The freezing and boiling point of a substance changes as the air pressure around it changes. for example, at a lower air pressure (higher altitude) it is easier for water molecules to escape from liquid into the air. in a high altitude city such as denver, colorado compared to a sea-level city such as houston, texas, water

What is the increase in density of a medium due to wave travel?