Answer:
F1 = ma = 5.5 kg * 10 m/s² = 55 N (force acts downwards)
F2 = - 50 N (force acts upwards)
net force = 5 N (downwards)
F = ma
a = F/m
a = 5 / 5.5
a = 0.91 m/s²
Step-by-step explanation:
Since the object is falling downwards, the air resistance acts upwards. We also have a force acting downwards since the rock experiences gravitational acceleration (the value of g above is 10 m/s² for the sake of easier calculation but you can also set it to be 9.81 m/s² which is the more accurate value). Since the air resistance and force due to gravity are acting in opposite directions and force is a vector, we have to put a minus in front of F1 or F2 (it doesn't matter which direction you chose to be the positive one) . Then we calculate the net force, aka the difference between F1 and F2. Finally, knowing the force and the mass, we can calculate the acceleration.