Answer:
A student carries a stack of books to the library - No work done the force to carry the books is perpendicular to the displacement. Thus, work done = F s cos 90° = 0
A shopping cart is pushed through a parking lot. - Work is done, as there is a force in the direction of the displacement of the cart.
A hockey puck slides on ice, with constant velocity. -No work is done. As the hockey puck is mongol with constant velocity, it means there is no acceleration-thus, no unbalanced force acting. When F = 0, W =0.
An airplane slows to a stop on a runway- negative work is done as the airplane is decelerating and moving on runway. When it stops, then there is no work being done but before that-yes.
A pool ball bounces off the edge of a pool table- work done. When pool ball bounces of the edge, it free falls under gravity in the direction of the force. Thus, work is being done.
