Longitudinal waves compress the medium they travel though. one example of a longitudinal wave is a

Waves in compressed string

Explanation:

Longitudinal waves are waves in which the vibration of the medium is going parallel to the direction of the waves produced by the medium.

Longitudinal wave can occur in compressed string. A compressed string displaced horizontally will transmit wave in the same horizontal direction. That's why they are longitudinal waves.

gravititional force is a force that is acting around you, it is non-contactable and it is a force that pulls you to the core of the earth.

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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.