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Work Problems

1. A sailboat is moving in the direction of the wind (see diagram below.) The wind exerts a constant force F as the boat moves a distance L. (a) What is the work done on the boat during this motion. (b) If the boat starts at rest and the drag force is negligible, what is the final speed of the boat?

2. The same sailboat now sails at an angle theta to the wind as shown in the diagram below and the wind exerts a constant force F. The distance traveled by the boat is L. (a) What is the work done on the boat during this motion. (b) If the boat starts at rest and the drag force is negligible, what is the final speed of the boat?

3.   A sailboat is tethered by a rope to a post so that it can move in an arc of a circle of radius L. The wind exerts a constant force F on the boat. (a) What is the work done by the wind on the boat as it rotates through 90°? (b) What is the work done by the tension in the rope during this motion? (c) If the boat starts from rest, what is its speed at the end of this motion?

 

4.   A force is one of the forces acting on a rocket that moves through a displacement .

(a) Find the work done by this force during the motion.

(b) Does this force try to make the rocket speed up or slow down? Explain.

5. (Cummings 9.35) A cold package of hot dogs slides rightward across a frictionless floor through a distance d = 20.0 cm while three forces are applied to it. Two of the forces are horizontal and have the magnitudes F_A = 5.00 N and F_B = 1.00 N; the third force is angled down by theta = -60.0° and has the magnitude F_C = 4.00 N.

(a) For the 20.0 cm displacement, what is the net work done on the package by the all the forces including the gravitational and normal forces?

(b) If the package of hot dogs has a mass of 2.4 kg and an initial velocity of 1.00 m/s to the right, what is its speed at the end of the displacement?