What you’ll learn5 learning objectivesChoose one objective for a focused lesson, or study the complete topic.4.5.1Scalar product• understand the concept of the work done by a force, and calculate the work done by a constant force when its point of application undergoes a displacement not necessarily parallel to the force cosWF d i=, Use of the scalar product is not required.Syllabus objective4.5.2Gravitational potential energy• understand the concepts of gravitational potential energy and kinetic energy, and use appropriate formulaeSyllabus objective4.5.3Forces• understand and use the relationship between the change in energy of a system and the work done by the external forces, and use in appropriate cases the principle of conservation of energy Including cases where the motion may not be linear (e.g. a child on a smooth curved 'slide'), where only overall energy changes need to be considered.Syllabus objective4.5.4Complex loci• use the definition of power as the rate at which a force does work, and use the relationship between power, force and velocity for a force acting in the direction of motion Including calculation of (average) power as Time taken Work done. P = Fv.Syllabus objective4.5.5Instantaneous acceleration• solve problems involving, for example, the instantaneous acceleration of a car moving on a hill against a resistance.Syllabus objective