Physics
posted by Aaron .
A model airplane of mass 0.9 kg is attached
to a horizontal string and flies in a horizontal circle of radius 5.2 m, making 1.2 revolutions
every 8 s. (The weight of the plane is balanced
by the upward “lift” force of the air on the
wings of the plane.)
The accelaration due to the gravity is 9.81
m/s2.
Find the speed of the plane

Huh ?
it is going (1.2 * 2 pi r) meters in 8 seconds
speed = distance/time = (1.2*2*pi*5.2)/8