the following forces are applied to an object f1 = 15 N [up], f2 = 10 N [right], f3 = 20 N [down]. Calculate the magnitude and direction of the net force.

Answer 1

In this problem we have multiple forces: two vertical forces as well as one horizontal force. 

Start with drawing all the forces on the object. Then,

First: Calculate the "net" vertical force (upward forces are positive and downward forces are negative):

=> Fy(net) = F1-F3

Second: Calculate the net horizontal force (positive if it's to the right): => Fx(net) = F2

Now, using trigonometry, the net force will be: Fnet = Sqrt(Fx(net)^2 + Fy(net)^2)

To find direction of the net force, you need to find the angle: Angle = arctan(Fy/Fx)

-MK

Answer 2