A big cannon shoots cannonballs the size of watermelons with an initial velocity of 132 MPH. The MythBusters team mounts the cannon on the back of a remote-controlled pickup truck. They plan to drive the
truck at about 13 MPH on a ?at surface in the desert. Under what angle relative to the ground do they
have to aim the cannon, so that the cannon ball lands back into the mouth of the cannon? Explain clearly
the choice of your reference frame!