2. A suitcase is hanging straight down from your hand as you ride an escalator. Your hand exerts a force on the suitcase, and this force does work. This work is (Cutnell & Johnson, 2012). a. positive when you ride up and negative when you ride down b. negative when you ride up and positive when you ride down c. positive when you ride up or down d. negative when you ride up or down 3. A person pushes a 16.0 -kg shopping cart at a constant velocity for a distance of 22.0 m . She pushes in a direction 29.0 below the horizontal. A 48.0 -N frictional force opposes the motion of the cart. Determine the following (Cutnell & Johnson, 2012): a. Magnitude of the force that the shopper exerts b. Work done by the pushing force c. Work done by the frictional force d. Work done by the gravitational force Knot The work done by a constant force on an object is the product of 0.5 the magnitude of the displacement d times the component of the force F parallel to the displacement, W = Fdcoso (eqn.1)