A person pushes a shopping cart with a force of 98 N acting down at 45°. If the cart travels at a constant speed of 0.8 m/s, what is the value of the combined retarding force acting horizontally on the cart due to friction and air drag? [Hint: It is the horizontal component of the force that drives the cart forward. The constant speed tells you that Fx = ma = 0.]

Question

anonymous · Answer

The value of the combined retarding force acting horizontally on the cart due to friction and air drag must be equal to de X component of the force 98N. 
$$\sum_{?}^{?}F= m*a=0$$ 
so

$$Fx- Fair-Ffriction=0$$
 then: 

Cos(45)* 98N = F air + F friction = 0,6995 N 
(action  equals minus reaction)

anonymous · Answer

I am still confused. 
What's the final answer? and why?

anonymous · Answer

Nevermind I got it :]
thanks