3.E.1.2 The student is able to use net force and velocity vectors to determine qualitatively whether kinetic energy of an object would increase, decrease, or remain unchanged.3.E.1.1 The student is able to make predictions about the changes in kinetic energy of an object based on considerations of the direction of the net force on the object as the object moves.The information presented in this section supports the following AP® learning objectives and science practices: Explain and apply the work-energy theorem.Explain work as a transfer of energy and net work as the work done by the net force. Then calculate the work done by these forces.Ī 10-N force is applied to push a block across a friction free surface for a displacement of 5.0 m to the right.By the end of this section, you will be able to do the following: For each case, indicate which force(s) are doing work upon the object. The following descriptions and their accompanying free-body diagrams show the forces acting upon an object. A free-body diagram is a diagram that depicts the type and the direction of all the forces acting upon an object. On many occasions, there is more than one force acting upon an object. Since F and d are in the same direction, the angle is 0 degrees.Ģ. The applied force must be 147 N since the 15-kg mass (F grav=147 N) is lifted at constant speed. The displacement is given in the problem statement. Thus, the angle between F and d is 30 degrees. It is shown that the force is 30 degrees above the horizontal. It is said that the displacement is rightward. The force and the displacement are given in theproblem statement. Since F and d are in the same direction,the angle is 0 degrees. It is said (or shown or implied) that the force and the displacement are both rightward. The force and the displacement are given in the problem statement.
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