Complete the sentence to define a reference frame. a reference frame is the from which an event is .

position
observed

A reference frame is the position from which an event is observed

Explanation:

In physics reference, frames or reference points are the positions where an observer is located and from that point can look at displacements, velocities accelerations of one or more bodies.

A classic example where this definition can be appreciated is some visitor to the airport who decides to travel along the airport treadmill in order not to continue walking, the speed of the band is 1 [m/s] at that time a child named Albert observes that a passenger urgently runs (3 m/s) through the same airport treadmill. The child located at a strategic point (frame of reference) observes that the passenger urgently moves at a total speed of (3 + 1) = 4 (m/s), while the person in the band sees the passanger approaching him at a speed of 3 (m/s). This demonstrates the use of reference frames.

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.