A 10 kg object is subjected to two forces F1 and F2. F1 has a magnitude of 20 N and acts straight upward and F2 has a magnitude of 30 N at 30 degrees below the horizontal from the positive x axis. a) Find the acceleration of the object.
b) A third force F3 is applied so that the object is in static equilibrium. Find F3.

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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.