1. The problem statement, all variables and given/known data A cart is moving horizontally along a straight line with a constant speed of 30m/s. A projectile is to be fired from the moving cart in such a way that it will return to the cart after the cart has moved 80m. At what speed and at what angle to the horizontal must the projectile be fired? 2. Relevant equations The kinematic equations. The problem ignores air resistance and friction. 3. The attempt at a solution The first thing I said in my answer to this problem was, "since the cart is moving at a constant velocity, for a projectile to land back on the cart it would have to be fired at 90 degrees to the horizontal". After stating this I could easily solve for the velocity. My professor however tells me that this is not true and that the angle will be less than ninety degrees.