powerpoint various phyiscal concepts

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For this assignment, you will create a PowerPoint that demonstrates the concepts covered in this unit. Find and select images that apply/explain/identify various physical concepts that we have learned in this unit. Identify the concept that is being demonstrated in that image, and provide an explanation that relates the image to the concept. Your presentation must contain at least these concepts:

  • How impulse-momentum theorem relates to Newton’s second law.
  • The relationship between linear momentum conservation and Newton’s third law.
  • How momentum conservation is exemplified in various physical activities.
  • The difference between kinetic and potential energy.
  • The relation among work, energy and power in daily life.

Some other topics that may be included are impulse, elastic/inelastic collision, energy conservation, power, work, angular momentum conservation, torque, center of mass/gravity, and centripetal/centrifugal force, among others.

Click here for a sample of what your PowerPoint may look like.

For a pdf version of this sample PowerPoint presentation, click here.

Your PowerPoint must be a minimum of 10 slides not including the title and reference slide. You are required to insert appropriate images and diagrams to enhance your content. In addition to the images, you must use at least two scholarly references in your presentation. Any images or information used should be cited in APA format. Also, it is a good idea to utilize presenter notes and provide narration, but this is not required.

UNIT III STUDY GUIDE Conservations of Momentum and Energy Course Learning Outcomes for Unit III Upon completion of this unit, students should be able to: 3. Explain Newton's laws of motion at work in common phenomena. 3.1 Relate impulse-momentum theorem to Newton’s second law. 3.2 Discuss the relationship between linear momentum conservation and Newton’s third law. 4. Explain the concepts and applications of momentum, work, mechanical energy, and general relativity. 4.1 Show examples of momentum conservation in various physical activities. 4.2 Distinguish between kinetic and potential energy. 4.3 Correlate the relation among work, energy, and power in daily life. Reading Assignment Chapter 6: Momentum Chapter 7: Energy Chapter 8: Rotational Motion Unit Lesson Impulse-Momentum Relation and Newton’s Second Law Momentum, or the linear momentum (p) of an object, is defined by its mass (m) times velocity (v): p=mv. Mass is an intrinsic property of an object, and it is the quantity of matter in the object. Mass is a scalar quantity and velocity is a vector, and thus, the direction of momentum is the same as the velocity points. Momentum can be related with force. The average force acting on a body can be obtained by the momentum change ∆p per a time interval ∆t. That is, = m= m ∆v/∆t=∆p/∆t. The product of and ∆t is the impulse J; J=∆t=∆p. The impulse equals the momentum change; this is the Impulse-Momentum theorem. The impulse-momentum theorem is a different expression of Newton’s second law (Cutnell & Johnson, 2004). Note that both are measured in [kg m/s=N s]. Suppose a stuntman is trying to jump from a tall building and he has a choice to land on sand or water. If he lands on water, his stopping time is much greater than if he lands on sand. The water exerts a smaller average force according to the impulse-momentum theorem because the sand and the water exert the same impulse on him to halt the motion. Therefore, he should land on water to diminish damage left on him. Linear Momentum Conservation and Newton’s Third Law The total linear momentum of a system without external forces is conserved, that is, constant. This is one of the most important and fundamental principles to support the action-reaction law of Newton. Suppose that there are two colliding balls, A and B, whose masses are mA and mB. There are two forces: the force exerted on A by B, FAB and the force exerted on B by A, FBA. According to Newton’s second law, the total force of this system is F= FAB + FBA. Notice that F is zero due to Newton’s third law; FAB = - FBA. That is, F= ma= m ∆v/∆t=∆p/∆t=0; momentum is constant (Cutnell & Johnson, 2004). The total momentum before collision is the same as the total momentum after collision; the total linear momentum is conserved. If it is not conserved, Newton’s law of action-reaction will be no longer valid. PHS 1110, Principles of Classical Physical Science 1 Example: Boxcar A whose mass m A = 5,000 kg and velocity vA = 1 m/s will link to boxcar B whose mass mB = 15,000 kg and velocity vB = 4 m/s. Find the final velocity V after they are connected. Assume that there is no friction in this system. A B A B Solution: According to the momentum conservation, the total momentum before linking, m AvA+ mBvB should be equal to the total momentum after linking, (m A+ mB)V. That is, V=(5000x1 + 15000x4)/20000=13/4= 3.25 m/s. Work, Energy, and Power Energy is a quantity assigned to one body that indicates that body’s ability to change the state of another body. Notice that energy is not a vector; it is a scalar. Heat is a good example of energy. If a hot object is in contact with a cold object, the hot object will warm the cold one. The quantity (½ m v2), where m is the mass and v is the velocity of the object, is defined as kinetic energy (KE) and its unit is the joule (J). The work done, W, on an object by a constant force F is defined as W=Fd, where, d is the displacement. For example, you ride an escalator with your shopping bag that is hanging straight down from your hand. Your hand exerts a force on the shopping bag, and this force does work. When the escalator goes up, the work is positive because the direction of force is equal to the displacement. On the other hand, the work done is negative when the escalator goes down because the force is opposite to the displacement. The result of work is a change in the kinetic energy of the object; W=Fd=mad=mv2/2 with zero initial velocity. When the force is originated from the gravity, W=mgd. The quantity (mgh), where h is the height of an object, is defined as potential energy (PE) and its unit is also joule (J). KE arose because of the motion of an object, while PE comes from the object’s height. The total mechanical energy, TE = KE + PE, is conserved; ½ mv2+ mgh=constant if the net work done by external non-conservative forces such as air resistance and friction is zero. TE is always the same value throughout the motion from the beginning to the end. Power (P) is work done per unit time. Its unit is J/s= watt (W); P=W/t= Fd/t=F v. That is, the average power is proportional to the average speed under the given force. Power is a scalar quantity because work and time are scalars. The unit W is originated from James Watt (1736~1819) who developed the steam engine. The familiar unit horsepower is also used. One horse power is equivalent to 745.7 W. Elastic and Inelastic Collision In general, there are two kinds of collision: elastic and inelastic collision. If the total kinetic energy of the system is conserved, it is called elastic collision. If it is not conserved, it is called inelastic collision (Cutnell & Johnson, 2004). In any case, the total linear moment is conserved. When two atoms collide, the total kinetic energy remains constant before and after the collision in most cases. This is an example of elastic collision. If the first atom gains kinetic energy, the second atom lost the energy. On the other hand, when two cars collide, the kinetic energy is lost mainly because of friction. The total kinetic energy is not constant in this inelastic collision. Torque Torque (T) is defined as the magnitude of the force (F) multiplied by the lever arm (d) in a rotational motion; T=Fd. Its unit is J; d is the perpendicular distance between the line of action and the axis of rotation. Let’s PHS 1110, Principles of Classical Physical Science 2 examine a case of torque exerted on a wrench with the same applied force (see Figure 8.20 on p. 139 in the textbook). Suppose the length of the wrench is 0.2 meters and the applied force is 100 N. If the force is exerted perpendicular to the wrench (the second picture in Figure 8.20), the produced torque is 100 x 0.2= 20 J. If you apply the force with an angle, the torque will be less than 20 J because the length of the lever arm will be shortened. The torque also can be expressed as the moment of inertia multiplied by angular acceleration for a rigid body rotating about a fixed axis. The moment of inertia varies along with the object’s shape and the location of the axis. Angular Momentum Conservation When an object rotates around an axis, the angular momentum (L) is the moment of inertia (I) multiplied by the angular velocity (w) of the object; L=Iw. The unit of w is in radian/sec and that of L is in kg m 2/s. If there is no external torque in the system, the total angular momentum is conserved. It is the analogous concept of linear momentum conservation. For an example, see Figure 8.52 on p. 151 in the textbook. Here is another example. A satellite is circling the earth. The major force exerted on the satellite is the gravitational force of the earth. The direction of this force points the center of the earth at any instant. Also, it passes through the axis about which the satellite rotates. There is no torque because of the gravitational force, and thus the angular momentum of the satellite remains constant. Angular momentum is an important physical concept because it is conserved in the Universe. Most astronomical objects—planets, moons, stars, and galaxies—have this property because they rotate and revolve. Angular momentum is the tendency of a body to keep spinning or moving in a circle. It can be transferred, but cannot be created or destroyed. For instance, in the Sun-Earth system, the Earth circles around the sun, and the magnitude of the angular momentum, (L), can be expressed in the formula L=mvr. Here, m is the mass of earth, v is the orbital velocity, and r is the distance between the sun and the earth. L must be conserved; i.e., the constant value. v increases as r decreases, and vice versa, with a fixed mass m. That is, v is inversely proportional to r. You might have noticed that an ice skater spins slower when his or her arms are extended and faster when his or her arms are drawn in. Similarly, the primitive giant gas cloud spins faster as more contractions occur, to conserve angular momentum. The cloud flattens along the rotational axis as time passes. The center part contracts into a ball of hot gas and dust, which is a protosun. The Sun evolved from the protosun. Planets are formed by accretions of gases outside the Sun. Circular Motion Consider an object moving in a circular orbit of radius (r) about a center of force. From symmetry, the speed (v) of the body must be constant, but the direction of the velocity vector is constantly changing. Such a changing velocity represents an acceleration a(=v2/r), which is the centripetal acceleration that maintains the circular orbit. In this circular motion, Newton’s third law plays an important role. A moving object has a tendency to keep moving with constant speed according to Newton’s first law. What is the driving force of this system? It is the centripetal (center-seeking) force to keep up the continuous circular motion. The direction of the centripetal force is inward. This is the action force. The reaction force is called the centrifugal (center-fleeing) force. The direction of the centrifugal force is outward. It is a fictitious force. If the object is released, that is, absence of the centripetal force, from the circular motion, it will fly out not because of the centrifugal force, but because of Newton’s first law. Reference Cutnell, J., & Johnson, K. (2004). Physics (6th ed.). Hoboken, NJ: Wiley. PHS 1110, Principles of Classical Physical Science 3 Suggested Reading The website below offers a more in-depth look at Newton’s third law. California Institute of Technology. (2013). Conservation of momentum. Retrieved from http://www.feynmanlectures.caltech.edu/I_10.html This video demonstrates elastic and inelastic collisions in an unusual atmosphere: space. Our Space. (n.d.). Momentum in space [Video file]. Retrieved from http://www.our-space.org/materials/statesof-matter/momentum-in-space To learn more about the work-energy principle, take a few minutes to explore the website below: Nave, R. (n.d.). Work, energy and power. Retrieved from http://hyperphysics.phyastr.gsu.edu/hbase/work.html Learning Activities (Nongraded) Nongraded Learning Activities are provided to aid students in their course of study. You do not have to submit them. If you have questions, contact your instructor for further guidance and information. To practice what you have learned in this unit, complete the following problems and questions from the textbook. The answers to each problem can be found in the “Odd-numbered Answers” section in the back of the textbook. The question number from the textbook is indicated in parentheses after each question. 1. Railroad car A rolls at a certain speed and makes a perfectly elastic collision with car B of the same mass. After the collision, car A is observed to be at rest. How does the speed of car B compare with the initial speed of car A? (Textbook #17 on p. 104) 2. When you jump from a significant height, why is it advantageous to land with your knees slightly bent? (Textbook #49 on p. 104) 3. Compared with a car moving at some original speed, how much work must the brakes of a car supply to stop a car that is moving twice as fast? How will the stopping distances compare? (Textbook #11 on p. 126) 4. What is the efficiency of a machine that miraculously converts all the input energy to useful output energy? (Textbook #21 on p. 127) 5. This question is typical on some driver’s license exams: A car that was moving at 50 km/h skids 15m with locked brakes. How far will the car skid with locked brakes if it was moving at 150 km/h? (Textbook #43 on p. 128) 6. On a playground slide, a child has potential energy that decreases by 1000 J while her kinetic energy increases by 900 J. What other form of energy is involved, and how much? (Textbook #77 on p. 129) 7. If a trapeze artist rotates once each second while sailing through the air and contracts to reduce her rotational inertia to one-third of what it was, how many rotations per second will result? (Textbook #49 on p. 155) 8. Dan and Sue cycle at the same speed. The tires on Dan’s bike are larger in diameter than those on Sue’s bike. Which wheels, if either, have the greater rotational speed? (Textbook #57 on p. 156) 9. You sit at the middle of a large turntable at an amusement park as it is set spinning and then allowed to spin freely. When you crawl toward the edge of the turntable, does the rate of the rotation increase, decrease, or remain unchanged? What physics principle supports your answer? (Textbook #91 on p. 158) PHS 1110, Principles of Classical Physical Science 4

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