Q. A cart is moving horizontally along a straight line with constant speed $30\, m / s$. 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 $80\, m$. At what speed (relative to the cart) must the projectile be fired $\left(\right.$ Take $\left.g=10\, m / s ^{2}\right):$
Motion in a Straight Line
Solution: