Question

A 250.-gram toy airplane has a battery and propeller. The propeller can propel the airplane forward at constant speed, but the plane does not move fast enough to have any measurable lift force. We'd like to know how fast the plane can move forward, but all we have available is a string and a tape measure. Emmie has an idea on how to find its speed. She hangs a string from the ceiling and attaches the other end of the string to the plane directly above its center of mass, so that the distance from the (fixed) point of attachment on the ceiling to the cm of the plane is 1.50 m. She then starts the plane moving. Once everything is stable, the plane travels in circles in a horizontal plane. Max measures the radius of the circle to be 0.75 m. What is the speed of the airplane?

Answer 1