Using a motion sensor,Susana finds that the acceleration of a 4-kg rock that has been dropped from the roof of a building is 6 m/s².She concludes that the magnitude of force of air resistance acting on the rock is approximately A)39.2 N B)24.0 N C)15.2 N D)9.81 N E)None of these is correct.

Question

Quizplus · Accepted Answer

Since the rock is dropping from the building, its initial velocity is 0. We can use the equation F_net = ma, where F_net is the net force acting on the rock, m is its mass, and a is the acceleration.

The force of gravity is pulling the rock down with a force of F_gravity = mg, where g is the acceleration due to gravity (9.81 m/s^2). So we have:

F_net = F_gravity - F_air resistance
ma = mg - F_air resistance
F_air resistance = mg - ma

Substituting the given values, we get:

F_air resistance = (4 kg)(9.81 m/s^2) - (4 kg)(6 m/s^2) = 39.24 N - 24 N = 15.24 N ≈ 15.2 N (rounded to two significant figures)

Therefore, the magnitude of the force of air resistance acting on the rock is approximately 15.2 N.

Using a Motion Sensor,Susana Finds That the Acceleration of a 4-Kg