Forces and Motion Content

1. Forces and Motion Content Competency Goal 4: The learner will conduct investigations and use appropriate technologies to build an understanding of forces and motion in technological designs. Alex Richardson Elementary Science Coach arichard@wsfcs.k12.nc.us

2. Background Concepts The motion of an object can be described by its position , direction of motion, and speed. The study of motion and forces that cause motion should provide concrete experiences for students.

3. Background Concepts (cont.) Students understand descriptions of moving objects and begin to describe forces acting on objects when simple objects are used. Force can be treated as the originator of motion. However, fundamental forces of nature should have an emphasis on gravitational force.

4. Background Concepts (cont.) The Earth’s gravity pulls on any object toward it without touching it. Gravitational force is an attraction between masses. The strength of the force is proportional to the masses and weakens rapidly with increasing distance between them.

5. Background Concepts (cont.) Changes in speed or direction of motion are caused by forces. The greater the force is, the greater the change in motion will be. The more massive an object is, the less effect a given force will have.

6. Background Concepts (cont.) How fast things move differs greatly. Some things are so slow that their journey takes a long time. Other things move too fast for people even to see.

7. Background Concepts (cont.) Integration of the concepts of forces and motion will increase student understanding. Measuring, graphing, and simple statistics are appropriate math connections. Technology integration can be achieved through collecting data and providing evidence.

8. Background Concepts (cont.) Social Studies integration can be achieved through exposing students to the historical development of the theories and laws used to explain forces and motion. Read and discuss biographical literature concerning the scientists responsible for the development of theories and laws to integrate Language Arts.

9. Background Concepts (cont.) Enrich learning for all students with forces and motion using nonfiction literature, fiction literature, and creative writing. Art and physical education can be used to assess student learning in certain activities in forces and motion.

10. Objective: 4.01Determine the motion of an object by following and measuring its position over time. • Many variables can affect motion such as: gravity, speed, time and direction. • A variable is anything that can change in an experiment. • Gravity is a force of attraction that exists between all objects.

11. Gravitational Concepts (cont.) • The force of gravity depends on the masses of two objects and the distance between them. (The Law of Universal Gravitation) • Gravitational force between two objects is greater when their masses are large. • The Earth’s mass is extremely large. As a result, the force of gravity between Earth and objects on Earth is very strong.

12. Speed and Time Concepts • The measure of how fast an object moves is its speed. • Speed measures the distance an object travels in a specific amount of time. • In order to find an object’s speed, take the distance and divide it by the time.

13. Speed and Time Concepts (cont.) • Speed can be measured using a stopwatch and a meter stick. • Velocity is the speed of an object in a particular direction. • The velocity of an object changes if either its speed or its direction of travel changes.

14. Direction Concepts • Direction is measured with a compass. • The points on a compass are N for North, S for South, E for East, and W for West. • To describe an object’s velocity, you must include both its speed and the direction it is moving. • You must use a stopwatch, a meter stick, and a compass to measure velocity.

15. Change in motion is observed or measured in reference to something else. • Changes in speed or direction of motion are caused by force. • Objects not in motion will continue in that state until acted upon by some force.

16. Objects in motion will continue along a straight line at a constant speed unless acted upon by some force. • The way to change how something is moving is to give it a push or a pull. • When more than one force acts upon an object , the forces may reinforce each other or cancel each other out.

17. Principles of Force and Motion

18. Newton’s First Law of Motion • This first law is often called the law of inertia. • An object at rest remains at rest unless acted on by an unbalanced force. • An object in motion continues to move at a constant speed in a straight line unless acted on by an unbalanced force.

19. Inertia • The tendency of an object to resist a change in its motion. Is Related to Mass • Objects with more mass have more inertia. • Objects with less mass have less inertia.

20. Newton’s Second Law of Motion • The greater the unbalanced force acting on an object , the greater the acceleration of the object. • Applying an unbalanced force to a smaller mass will produce a greater acceleration on the object than the same force applied to a larger mass. • Force is inversely proportional to mass.

21. Newton’s Third Law of Motion • This law is often called the law of action and reaction. • Forces come in pairs. • Whenever one object exerts a force on a second object, the second object exerts a force on the first object that is equal in magnitude and opposite in direction. • Action/reaction force pairs don’t always cause motion.

22. Momentum • Momentum is an example of Newton’s third law of motion. • Momentum is a measure of how hard it is to stop a moving object. • The momentum of a moving object depends on its mass and velocity.

23. Momentum (cont.) • As mass and velocity increase, so does momentum. • Action and reaction forces result in momentum being transferred from one object to another when objects collide. • One object may gain momentum while another loses momentum. • The total amount of momentum remains the same in every collision.

24. Objective: 4.02 Evaluate how pushing or pulling forces can change the position and motion of an object. • Force is pushing or pulling of an object that results in a change in motion. • Force is one of the measures of the relationship between objects. • Force is action on an object that causes its momentum to change.

25. Force acting on an object in motion will speed it up, slow it down, or change its direction. • Force can cause an object at rest to start moving. • Forces that push or pull can result in a change in direction or speed of a motion.

26. Forces can work together or against each other. • Balance and unbalance in pulling and pushing can change the direction of the object and or the quality of the motion such as fast, slow, and etc.

27. Objective: 4.03 Explain how energy is needed to make machines move. (moving air and gravity). • The sun is the primary source of all energy. • Energy moves from one source to another. • Energy cycles through living as well as nonliving things.

28. Energy is needed to make machines move or make machines operational. • Air movement and gravity are two forces that cause motion to occur. • Energy is never created nor destroyed.

29. Each form of energy can be converted. • It simply changes from one form to another. • All forms of energy may be either potential or kinetic.

30. Potential energy is stored energy. • The higher above ground an object is and the greater its mass, the more potential energy it has. • Kinetic energy is energy associated with motion. • The faster an object moves and the greater its mass, the more kinetic energy it has.

31. Energy is found in many forms.AC HELMS is a mnemonic that will help capture the forms of energy. A - Atomic C - Chemical H - Heat E - Electricity L - Light M - Motion S - Sound

32. Objective: 4.04 Determine that an unbalanced force is needed to move an object or change its direction. • Forces that are not equal and opposite are unbalanced. • Force includes any push or pull that results in the motion of an object. • An unbalanced force influences the objects movement.

33. Unbalanced Forces (cont.) • An unbalanced force causes an object to change its speed of an object already in motion. • An unbalanced force is the exertion of more force from one direction than from other directions. • An unbalanced force causes an object to be set in motion or change its direction.

34. Unbalanced Forces (cont.) • An object can have more than one force acting on it. • If the sum of all forces acting on an object are unbalanced, they can make objects at rest start moving, or moving objects change their direction or speed.

35. Balanced Forces • Balanced forces are equal and opposite. • Balanced forces cancel each other out, so motion does not change. • If an object is at rest , it will remain at rest. It it is in motion, it will remain in motion. • If any forces acting on an object are balanced, the net force is zero.

36. Objective: 4.05Determine factors that affect motion including: Force, Friction, Inertia, and Momentum. • Force is the pulling or pushing that results in a change in the motion, size, or shape of an object. • Friction is a force that creates resistance in the motion of two surfaces rolling, rubbing, sliding, pulling or pushing against each other.

37. Friction • Friction works against motion. • Friction is produced when two objects come in contact with each other. • The amount of friction two objects produce depends on how rough the objects are.

38. Friction (cont.) • If the objects are rough, they produce more friction as they rub against each other. • If the objects are smooth, they produce less friction as they rub against each other. • Friction depends on how hard two objects are pushing against each other.

39. Inertia and Momentum • Please review Objective: 4.01Determine the motion of an object by following and measuring its position over time. • Review content concepts 19, 22, and 23.

40. Objective: 4.06Build and use a model to solve a mechanical design problem. Devise a test for the model. Evaluate the results of test. • Problems and solutions can be identified. • Designing solutions may also have constraints and barriers that need to be resolved. • Suitable tools and technologies need to be used to reach a successful outcome.

41. Many design processes are used to come up with a solution to a problem. • Design requirements specify how a product must perform. • Engineers develop, modify, and improve designs to meet specific requirements of a product.

42. Solutions should be identified for their effectiveness in responding to the problem. • Solutions to a problem may be accomplished by modifying something that already exists. • Appropriate tools are used to help make better decisions based on observation, measurements, and ease of work.

43. Various ways to demonstrate the effectiveness or drawbacks of a solution • Design a computer model to predict what would happen in different situations. • Perform a demonstration to see how the design works and record observations. • Use previously collected data on the design such as written observations, drawings, and class discussions.

44. Objective: 4.07 Determine how people use simple machines to solve problems. • Machines range from simple to complex. • A simple machine is a tool that makes work easier. • A complex machine is made up of simple machines. • The use of machines are reflected in every aspect of our lives and on a daily basis.

45. The greater the force and the greater the distance the object moves, the more work is done. • Work happens when a force moves an object through a distance. • Work equals force times distance: W= F x d

46. Machines are used in reducing the amount of effort needed to complete a task. • Most simple machines let you use less force to move an object. • When you use less force, you have to apply it for a longer distance.

47. Some simple machines let you move an object a longer distance. You have to apply more force , but you can apply it for a shorter distance. • With any kind of simple machine, the amount of work you do doesn’t change. • What changes is the amount of force you apply and the distance you apply it.

48. Six Basic Kinds of Simple Machines • Inclined plane • Wedge • Screw • Lever • Wheel and axle • Pulley

49. Inclined Plane • An inclined plane can reduce the amount of force needed to move a heavy object. • An inclined plane is a flat surface that slopes. • You apply less force, but you have to apply it for a longer distance.

50. Wedge • A wedge can reduce the amount of force needed to split apart objects. • A wedge is an incline plane that moves. • You have to apply force for a longer distance when you use a wedge. • A wedge moves the object’s pieces a short distance.