Transcript energy
Energy, Forces, and Motion A Science Module for Grades 3-5 Excellence in K-8 Science: A NC MSEN Statewide Initiative Instructors: Beth Brampton, New Hanover County Schools Dennis Kubasko, UNC Wilmington Organizing Topics • In the early grades of science education it is imperative to provide an experiential approach to energy, forces, and motion. It is important to develop accompanying vocabulary as it becomes relevant to the students through their experiences. A more in-depth theoretical understanding of energy, forces, and motion need not be undertaken until middle school. Relevant context • Relevant Content in the National Standards Document • Relevant Goals and Objectives from the North Carolina Standard Course of Study • Integration across the curriculum • Module Overview of Science Background for Instructors • Energy, Forces & Motion Dictionary Learning Cycle 1: Investigating Force and Motion Questions: •What is a Force? •What is Motion? •How are they related? Introduction • These investigations use the concepts of force • and motion to develop an initial understanding of energy basics. Through an observation of motion of some familiar toys, students will develop the vocabulary necessary to answer the following questions: – How does the toy’s motion change? – What forces are acting on the toy? – Where does the energy come from? Where does it go? Instructional Strategy • Engage – The Domino Theory, Thumper Activity • Explore – Energy Toys Learning Center • Explain – Cartoon • Elaborate – Motion Detectors • Evaluate – Roller Coaster • Making Connections Science Background Information • Observation of the motion of simple toys will expose students to the concepts of potential and kinetic energy, forces (such as gravity and friction), velocity, acceleration, inertia, Newton’s Laws of Motion, and conservation of energy. 1st Law or the Principal of Inertia: • If an object is left alone, not disturbed, it continues to move with constant velocity in a straight line (if it was originally moving) or it continues to stand still (if it was just standing still). Engage • The two kinds of energy are stored energy (Potential) and moving energy (Kinetic). • The classic domino rally stores up energy or gains potential energy as the dominos are set up. As they fall they have moving or kinetic energy. Engage • Thumper is a model for the magic trick where • • the table cloth is pulled off the table while leaving the dishes on the table. If the table cloth is pulled off rapidly, the dishes remain in place (inertia) because the force (a push or pull) is not transferred from the table cloth to the dishes. If the table cloth is pulled out slowly, then friction will transfer the force to the dishes and all will fall off the table. Explain • In groups of 2-4 teachers explore the motion of the group of toys. Please be encouraged to try out all of the toys. Each group should analyze the motions of the toys. – How did you start the toys to move? What was the push or pull? – What did the toy do? Did it roll, bounce, slide, etc.? – What happened just before the toy stopped moving? – What do you think makes the toy stop? Explore • Tops -- The principle of rotational inertia states • • • that a spinning object will continue to spin unless acted upon by an outside torque (circular force). A spinning top on a level surface spins around its axis and does not fall. Spinning the top produces rotational inertia (amount of spin and the direction of spin) which keeps it in place as it rotates. The forces which cause it to stop rotating, and therefore fall, are friction (between the table and top) and air resistance. Explore • Rattlebacks have a counterclockwise spin bias that results from the shape of the smooth ellipsoidal bottom and the distribution of the mass with respect to the axis of spin. The long axis of the ellipsoid is aligned at an angle of 5 to 10 degrees to the long axis of the flat top. Just prior to reversing direction, a Rattleback rocks up and down on its long axis, hence the name. Explore • Topsy-Turvy or Mushroom Tops will invert if there is sufficient angular inertia. If the top is spun fast enough the stem of the top will touch the surface of the table. If the stem touches, slides across the surface and the top is still moving fast enough, the friction can enable the top to flip and continue to spin on the stem. Explore • Spring-Ups – Energy is stored as elastic potential energy in the toy's spring when the energy of your muscles pushes down on the toy (compressing the spring) and makes the suction cup stick. When the suction cup lets loose, the elastic potential energy in the spring is converted to kinetic energy. The toy has the most kinetic energy when the spring is completely expanded. As the toy jumps, the kinetic energy is being changed into gravitational potential energy. Explain • Spring-ups often have a flipping motion because • the spring bends slightly as the suction cup releases. As a result, the force exerted is not perfectly vertical. At its highest point, almost all of the toy's kinetic energy is converted into gravitational potential energy. As the toy comes back down, the gravitational potential energy is converted back to kinetic energy. When the toy hits the table and stops, it loses both its potential and kinetic energy. Where does the energy go? Primarily, it becomes heat (energy), but some of it goes into sound (energy). Explain • Wind-up toys -- The energy is supplied by human • • muscles winding the spring. This energy is stored in the spring as elastic potential energy and is stored there until you release the winder. Then the potential energy is converted to the kinetic energy of the toy's movement. The toy moves, and its internal parts also move. Both of these movements involve kinetic energy. This toy has the most potential energy when you have finished winding the winder and haven't yet released it. The toy has the most kinetic energy when it is moving fastest ----- somewhere in the middle of the motion. The force of friction between the tires and the floor causes the toy to slow down and eventually stop. The friction of the moving internal parts of the toy also contributes to the slowing and stopping of the toy. The toy's kinetic energy is turned into heat (energy) - the toy and the floor each get a little warmer. Explain • Balls -- A ball held at some distance above the ground possesses gravitational potential energy from the force needed to lift the object against gravity (force). When it is released, it falls and gains kinetic energy and loses potential energy. • When the ball collides with the floor, some of this kinetic energy is stored as elastic potential energy in the ball and the floor. The particles in the ball and the floor squeeze together like tiny springs. How well the material in the ball springs back to its original shape after being deformed determines the height of the rebound. • If the material absorbs the potential energy and returns to its original shape slowly or not at all, much of the energy is not returned to the motion of the ball, resulting in a low bounce. The collision is said to be inelastic. Evaluate • Make a roller coaster that will have the following elements: hill, turn and loop. State a time limit, work in groups. The expectation is that they will explain the order of the elements, energy input and output, problems encountered, and how well were expectations met. Making Connections • A real life connection would be automobile accidents. Forces, motion and energy transfer have very graphic results. The type of car (mass), and the speed of the vehicle will determine the forces applied. The condition of the road, if it is icy, wet, sand, etc., would bring friction into the discussion.