(a) An automobile driver, stopped at an intersection, ties a helium-filled balloon on a string attached to the floor of her car, so the balloon floats up. When the light turns green she accelerates the car forward. Relative to the car, does the balloon move forward, backward, or remain vertically above the place it is tied?

(b) A rectangular fish tank is half filled with water. One end of a rubber band is attached to the bottom of the tank, and the other end is attached to a cork that floats on the water's surface, as shown in the diagram. Now the tank is pushed to the right, giving it a constant rightward acceleration. Eventually, the water surface, cork, and rubber band settle into a new equilibrium configuration. Sketch this new configuration.