What type of wave has particles push together and pull apart?

when wave propagate through the medium the medium particles have two type of possible motions

1) Transverse Waves : here medium particles will move perpendicular to wave propagation and they pull and push perpendicular to the length

2) Longitudinal wave : here medium particles will move to and fro along the length of the medium and the medium particles will push and pull together along the length of the string.

So here in two types of wave motion it will depends on the medium type as well as it will depend on the source how is wave produced.

So the given type of wave in which particles push together and pull apart the wave must be longitudinal wave.

firearm identification is the process of analyzing the bullets and cartridge cases left at a crime scene to determine if they came from a particular firearm. marks on the bullets and cartridges may be common to every firearm of that type. these are called class characteristics.

air exerts forces on falling objects near earth’s surface.

explanation:

the term 'free falls' refer to object that are falling towards the earth, in a situation in which gravity is the only force acting on the object.

for an object in free fall, the acceleration is constant (g, the gravitational acceleration), and so the velocity of the object constantly increases.

for objects near earth's surface, there is always another force acting on the object: the resistance due to the air. this force is opposed to the direction of fall of the object, and it is proportional to the velocity of the object, so as the object falls down, this force increases up to a point when it balances the force of gravity, and the object continues its motion at constant velocity (called terminal velocity). since in this case gravity is not the only force acting on the object, we are not in a situation of free fall.