Calculating Work Done by Forces on a Moving Object

[alex7298]

Homework Statement

A oerson pushes a 16.0kg shopping cart at a constant velocity for 22.0m at an angle of 29 degrees below the horizontal. A 48.0N frictional force opposes the motion of the cart.
a)what is the magnitude of the force the shopper exerts on the cart.
Determine the work done by b) the pushing force, c) the fricitonal force, and d) the gravitational force

Homework Equations

W=(Fcostheta)d
W=Fd

The Attempt at a Solution

well I am not sure where to start because using the equation W=(Fcostheta)d leaves you with two variables.
any help would be appreciated

 

[Supernats]

Well, what does that constant velocity tell you about total force?

 

[alex7298]

F=ma
so the net force would be zero, which doesn't make sense because the cart is going forward, so wouldn't there have to be a force greater than the one that opposes it?