A frictionless cart in the shape of a right triangle (with the vertical side forward) is elastically
impacted by vertically falling raindrops. The speed of the cart as a function of time can be
analytically deduced as an exercise in the use of trigonometric and hyperbolic functions. A
characteristic time defines the approach to a terminal speed which is a sizeable fraction of the
speed of the rain. The treatment is accessible to a student in a calculus-based mechanics course.