An iceboat of mass M = 250 kg sits motionless on a frozen lake. The boat is tied to a stake by a rope of length R = 100 m. A steady wind starts to blow from the West, pushing the boat with a constant force F = 150 N. The boat slides without friction along the ice, moving in a circular arc as the rope stretches taut.

How fast is the boat moving when it reaches the point marked "X"?

Please try to do this problem by breaking the motion of the boat along the arc into a number of little steps; assume that each little step is a short, straight line.

• draw a picture of the boat when the rope has swung through some angle theta from its starting position
• determine the angle between the force of the wind, and the direction of the boat's motion at this point
• figure out the work done by the wind as the boat moves by a little step in this direction
• write an expression for this work -- it should include a sine or cosine of the angle theta, as well as a factor of dtheta
• integrate the work as the boat moves from theta = 0 to theta = 90 degrees.