Force and Motion
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1) Sir Isaac Newton studied motion and is best known for his laws of motion and universal law of gravitation. 2) Forces can cause objects to start or stop moving, change direction, or maintain constant motion depending on whether the net force is balanced or unbalanced. 3) Friction opposes the motion of objects in contact and depends on factors like the nature of the surfaces and the pressing force between them. It exists as both static and kinetic forms.
Force and Motion
- 3. Getting to Know Sir Isaac Newton Origin/ Background Branch of Science How did he change the world for the better? Best known for: Why is it important to get know Sir Isaac Newton through his work? What does this knowledge tell you about the study of motion?
- 4. The Natural of Force FOCUS POINTS: Explain how balanced and unbalanced forces are related to motion. Describe friction and identify the factors that determine the friction force between two surfaces.
- 5. Stack several metal washer on top of a toy car. Place a heavy book on the floor near the car. Predict what will happen to both the car and the washers if you roll the car into the book. What might be the reason for any difference between the motion of the car and the washer?
- 7. Forces and Motion Aristotle's view of motion is "it requires a force to make an object move in an unnatural" manner - or, more simply, "motion requires force".
- 8. Galileo’s studies of falling and rolling objects showed that the natural tendency of an object was to continue moving at a constant rate in straight line, and that no force was needed to sustain its motion. He reasoned that the object would stop moving due to a frictional force, which when eliminated would cause the object to remain in motion, unless it encountered an external force.
- 9. Force- as a push or pull acting upon an object as result of its interaction with another object. Carriage being pulled by a horse or a game of tug- of- war when two opposing teams are pulling on the ropes.
- 10. What changes can force do to motion? 1. Forces can make an object move starting from the rest position. 2. Force can make a moving object stop. 3. Force can change the direction of a moving object.
- 11. Whenever an object moves from a rest position, its velocity increases; if its stops, then its velocity decreases. When it changes direction, the objects velocity also changes. The direction of motion depends on the direction of the applied force.
- 12. Force is the quantity which is measured using a standard metric unit known as the newton (N). One newton is the amount of force required to give a 1-kg mass an acceleration of 1 m/s. 1N + 1kgm/s
- 13. A force may not always cause an object to move, especially if there is more than one force present. This single force that acts and causes a change in the state of motion of an object is known as the net force of the resultant force. The resultant force is the vector sum of all forces acting in an object.
- 14. If no changes in state of motion are produced, these forces are said to be balanced force. If there is a net force, then this force is said to be unbalanced force.
- 15. Suppose you and a friend are playing tug-of-war , and you are both pulling the opposite ends of the rope. You are pulling the rope toward you with a force of 5N while your friend is pulling toward the opposite direction with the same force of 5N. What is the net force on the rope?
- 16. Types of Forces Forces can be classified into two basic types based on how are applied or how they act on the other objects. Contact Forces- forces that require physical contact Non-contact force or action-at-a-distance force or field force- does not require physical contact to have any effect on the other object.
- 17. Examples of contact forces Applied force Normal force Frictional force Air resistance force Tensional force Spring force
- 18. Non- contact force Gravitational force Electrical force Magnetic force
- 19. Contact Forces Applied force (Fapp) - An applied force is a force applied to an object by another object or a person. The direction of the applied force depends on how the force is applied Normal Force (N) - Is the support force extend upon an object that is in contact with another stable object. Sometimes referred to as the pressing force.
- 20. Frictional Force (f) - The force exerted by the surfaces in contact with each other and move relatively being pressed with each other. The friction force opposes the motion of an object. The friction force can be calculated using the equation: f= µN. Where µ is the coefficient of friction and N is the normal force
- 21. Air Resistance Force (Fair) - Is a special type of frictional force that acts on objects as they travel through the air. Like all frictional forces, the force of air resistance always opposes the motion of the moving object. ( Skydiver or downhill skier) Tensional Force ( T) Is transmitted through a string, rope, or wire when it is pulled tight by forces acting at each end. Spring Force (Fstring) Is the force exerted by a compressed or stretched spring on my object that is attached to the string.
- 22. Non-contact Force Force of Gravity (also known as Weight, W) - Is the force with which the Earth, moon, or other massive body attracts an object toward itself. - This force on an object on Earth is always equal to the weight of the object as given by the equation: W=Mg, where g is the acceleration due to gravity which has a value of 9.8m/s² (on Earth) and m is the object’s mass (in kg)
- 23. Electrical Force - The force that exists between charges. It can either be attractive or repulsive force. Magnetic Force -Force that exists in magnets. It is the force that makes magnet attract or repel objects or other magnets
- 24. Free- Body Diagram Forces can be seen based on how they acted on an object. Forces acting on an object can be shown by representing them as arrows. This representation is called a Free-Body Diagram (FBD). An FBD is a diagram showing all the known and unknown forces acting on the object indicating their magnitudes and directions.
- 27. Friction Friction is a force that opposes the sliding of the surface across an adjacent surface. It acts parallel to the surface and opposite in direction of its sliding motion.
- 32. Two factors affecting Friction One is the material’s ability to form attractive forces that cause the two surfaces to stick together during a close contact– the nature of the material. The second pertains to how tightly the materials are pressed together causing an interlocking actions in the irregularities of the surfaces in close contact—the degree to which the materials are pressed together.
- 33. When dealing with frictional force, the following must always be remembered: 1. Frictional force is acting along the surface of contact and is opposite the direction of motion 2. It is directly proportional to the normal force or the force pressing the bodies together. 3. It does not depend on the area of the surface in contact. 4. Provided the speed is not very high, sliding friction does not depend on the speed of motion. 5. Friction depends on the nature of the surfaces in contact.
- 34. Two Kinds of Friction Static Friction- is the force of friction present on objects in contact with each other but are not moving.
- 35. Kinetic Friction- is the kind of friction that is present on objects that are moving. 2 kinds of kinetic 1. sliding friction 2. rolling friction