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Topic 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 Displacement Vectors Kinematics Graphs Energy Power Springs Shadows Field of Vision Colors Concave mirrors Convex mirrors Refraction Lenses Optical Power Slides Minutes 9 27 13 39 13 39 10 30 10 30 5 15 4 12 3 9 7 21 3 9 7 21 4 12 5 15 10 30 6 18 Energy is the capacity to do work Just like money is the capacity to purchase There are three types of work that can be done. (We see the object going faster) (We see the object going higher) (We can feel the heat and hear the sound) In an idealIf system, there is being no friction and thusnot nobeing work is done an object is not accelerated, raised, to overcome friction (no energy and there is no friction (ideal), noloss). work is done. Accelerate Raise Overcome friction “Constant velocity” f The force must be parallel to the distance. Accelerate Raise Overcome friction “Constant velocity” The vertical component makes the object lighter by 86.7 N. f = 50.0 N 100 N Cos 60 Since the object is moved at constant velocity, the work (energy) goes to overcome friction and the energy is lost. Accelerate Raise Overcome friction “Constant velocity” The vertical component makes the object lighter by 64.3 N. f = 76.6 N 100 N Cos 40 Since the object is moved at constant velocity, the work (energy) goes to overcome friction and the energy is lost. Accelerate Raise Overcome friction In this case, all the applied force goes to do the work and it is the most efficient method to pull the object. If the object is moved at constant velocity, the work (energy) goes to overcome friction and the energy is lost. If the object is accelerated, the work (energy) goes to the object in the form of kinetic energy. No friction (no energy loss) Example (1 N)(100 m) = 100 J Energy in 100 J in IMA = 100 100 J out Energy out (100 N)(1 m) = 100 J As illustrated below, there are two families of simple machines each family consists of three types of machines: Click Don’t confuse weight with mass! A hammer falls from a scaffold and 1.5 s later strikes the ground with a kinetic energy of 157.5 J. What is the weight of the hammer? Click Work Slide: 5. 1 In flattening the ground of a tennis court, Robert uses a 20 kg roller as illustrated below. If Robert pushes the roller a distance of 10 m with an applied force of 200 N, how much work does he do? . Click Work Slide: 5. 2 In flattening the ground of a tennis court, Robert uses a 20 kg roller as illustrated below. If Robert pulls the roller a distance of 10 m with an applied force of 200 N, how much work does he do? Click Work Slide: 5. 3 In flattening the ground of a tennis court, Robert uses a 20 kg roller as illustrated below. Pushing Pulling Which is easier to do, push or pull the roller? It is easier to pull since in pulling the vertical component of the pull is upward thereby reducing the weight. However, it is more effective to push the roller as the vertical component will increase the weight. Click Kinetic Energy Slide: 5. 4 A 20 g bullet has a velocity of 25 000 cm/s. Calculate its Convert grams to kilograms Convert cm/s to m/s kinetic energy. 20 g = 0.02 kg 25 000 cm/s = 250 m/s Click Kinetic Energy Slide: 5. 5 An object having a mass of 5 kg is traveling at 6 m/s. It accelerates to a velocity of 12 m/s. How much work was done to accelerate the object? Click Potential Energy Slide: 5. 6 A 2 kg mass, moving horizontally at 10 m/s, slides up a frictionless incline as illustrated in the diagram below. How high up the incline does the mass rise? Click Potential Energy Slide: 5. 7 Starting with an initial velocity of 10 m/s, a 2 kg object slides down a frictionless shoot as illustrated in the following diagram. How high up the incline does the mass travel before coming to a stop? Click Machines Slide: 5. 8 Which one of the following simple machines cannot be used to lift a 100 kg load by applying a force less than 980 N? A) I B) I and III C) I and IV D) I, II and IV Click Machines Slide: 5. 9 Betty uses the hoist illustrated on the right to raise a mass of 200 kg. If she can pull the rope 5.0 metres in a time of 10 seconds, what is Betty’s power output? Note: Disregard friction. A) 17.0 W I.M.A. = 6 (6 ropes) B) 100 W C) 163 W D) 980 W Click Machines Slide: 5. 10 Which two of the following simple machines have the same ideal mechanical advantage? 1 2 IMA = 5 3 A) 1 and 2 IMA = 4 4 B) 1 and 4 C) 2 and 4 D) 3 and 4 Click … and good luck!