Question

part 2: for each free body diagram, 1) determine the net force, 2) determine whether it is balanced or unbalanced, explaining why.
free body diagram net force balanced or unbalanced? why?
f_norm = 20 n
f_grav = 20 n
f_air = 40 n
f_grav = 25 n
f_norm = 3 n
f_frict = 5 n f_app = 5 n
f_grav = 3 n
f_norm = 3 n
f_frict = 5 n
f_grav = 3 n

Explanation:

Case 1:

Step1: Calculate net - force in vertical direction

The normal force $F_{norm}=20\ N$ acts upwards and the gravitational force $F_{grav}=20\ N$ acts downwards. The net force $F_{net}=F_{norm}-F_{grav}=20 - 20=0\ N$.

Step2: Determine balance

Since $F_{net}=0\ N$, the forces are balanced because the sum of all forces acting on the object is zero.

Case 2:

Step1: Calculate net - force in vertical direction

The air - resistance force $F_{air}=40\ N$ acts upwards and the gravitational force $F_{grav}=25\ N$ acts downwards. The net force $F_{net}=F_{air}-F_{grav}=40 - 25 = 15\ N$ (upwards).

Step2: Determine balance

Since $F_{net}
eq0\ N$, the forces are unbalanced because there is a non - zero net force acting on the object.

Case 3:

Step1: Calculate net - force in vertical direction

The normal force $F_{norm}=3\ N$ acts upwards and the gravitational force $F_{grav}=3\ N$ acts downwards. In the vertical direction, $F_{nety}=F_{norm}-F_{grav}=3 - 3=0\ N$. In the horizontal direction, the applied force $F_{app}=5\ N$ acts to the right and the frictional force $F_{frict}=5\ N$ acts to the left. So, $F_{netx}=F_{app}-F_{frict}=5 - 5 = 0\ N$. The net force $F_{net}=\sqrt{F_{netx}^{2}+F_{nety}^{2}}=0\ N$.

Step2: Determine balance

Since $F_{net}=0\ N$, the forces are balanced because the sum of all forces in both horizontal and vertical directions is zero.

Case 4:

Step1: Calculate net - force in vertical direction

The normal force $F_{norm}=3\ N$ acts upwards and the gravitational force $F_{grav}=3\ N$ acts downwards. In the vertical direction, $F_{nety}=F_{norm}-F_{grav}=3 - 3=0\ N$. In the horizontal direction, there is a frictional force $F_{frict}=5\ N$ acting to the left and no opposing horizontal force in the right direction. So, $F_{netx}=5\ N$ (to the left). The net force $F_{net}=\sqrt{F_{netx}^{2}+F_{nety}^{2}} = 5\ N$ (to the left).

Step2: Determine balance

Since $F_{net}
eq0\ N$, the forces are unbalanced because there is a non - zero net force acting on the object.

Answer:

Free Body Diagram	Net force	Balanced or Unbalanced? WHY?
	$15\ N$ (upwards)	Unbalanced. Non - zero net force as $F_{air}>F_{grav}$
	$0\ N$	Balanced. Net force in both horizontal and vertical directions is zero
	$5\ N$ (to the left)	Unbalanced. Non - zero net force in the horizontal direction