Newton's Second Law: Calculating Net Force on a Wagon with a Child (28.5kg)

[Mathcaptor]

A wagon carries a child. Together mass is 28.5kg. You pull on the handle of the wagon at an angle of 40degrees from the horizontal. The wagon travels over a level horizontal sidewalk. A force of friction of 12.0N acts on the wagon.

a) What is the net force acting on the wagon?



Note: I'm really having trouble with calculating this (triangle wise). Please help ASAP.

 

[Carid]

There's a force W operating vertically downwards. It's the weight of the trolley.
There's a force F pulling on the trolley. All I know about that force is that the horizontal component is sufficient to overcome a 12N frictional force.
So build a right angled triangle with a 40° angle in it to represent the force vectors. The hypotenuse is length F (unknown for the moment). The force adjacent to the 40° angle is length 12. Now can you calculate F?

Then you need to do the vector addition of W and F to find the net force.
The angle between F and W will be 90° + 40°.