Answer:
0.164 N
Explanation:
Newton's second law: sum of the forces equals mass times acceleration.
∑F = ma
F − mg = ma
a = (F − mg) / m
In real life, air resistance is a function of velocity. But we will assume that it is constant.
Given:
y₀ = 20 m
y = 0 m
v₀ = 0 m/s
v = -8 m/s
Find: a
v² = v₀² + 2a (y − y₀)
(-8 m/s)² = (0 m/s)² + 2a (0 m − 20 m)
a = -1.6 m/s²
Therefore:
-1.6 m/s² = (F − 0.020 kg × 9.8 m/s²) / 0.020 kg
F = 0.164 N
Round as needed.
