force and motion.pdf
- 1. Unit 1 Motion Lesson 1 The nature of force
- 2. FORCE AND MOTION Balanced and Unbalanced Forces Velocity and Acceleration
- 4. Motion • What is motion? • A change in the position of an object over time.
- 5. Overview • Galileo was successful in providing an experimental and theoretical background on how to describe motion. • Newton who answered and explained why objects move and why they accelerate. • Newton’s Laws of Motion
- 6. • What causes an object to move? - A force • What is force? - Is define as a push or pull acting upon an object.
- 7. Example: 1. A game of tug-of-war wherein two opposing teams are pulling on the ropes. 2. Pushing a cart at the supermarket.
- 8. Aside from seeing force as simple push and pull, force can be viewed as any influence capable of producing a change in the state of motion. • How do you know if something is in motion or has moved? • What changes can force do to motion?
- 9. 1. Force can make an object moved starting from rest position. 2. Force can make a moving object stop. 3. Force can change the direction of a moving object.
- 10. ➢ Whenever an object moves from a rest position, its velocity increases. ➢ If it stops, then its velocity decreases. ➢ When it changes direction the velocity also changes.
- 11. ➢ A change in the state of motion means change in velocity. ➢ Whenever velocity changes with respect to time, acceleration produced. ➢ A change in state of motion means a change in velocity or simply the occurrence of acceleration.
- 12. ➢ Velocity, acceleration, and force are vector quantities. ➢ It must have magnitude and direction. ➢ Force is a quantity which is measured using a standard metric unit known as “ newton (N)”.
- 13. ➢ 1 newton is the amount of force required to give 1-kg mass an acceleration of 1 m/s². ➢ 1N = 1 kg m/s²
- 14. ➢ A force may not always cause an object to move, especially if there is more than one force. • What will happen if there is a presence of another force?
- 15. ➢ The presence of another force may cancel the effect of the other force; causing no change in the state of motion of an object. ➢ If a single force is present, it can cause a change in the state of motion.
- 16. ➢ Single force that acts and causes a change in the state of motion of an object is known as the net force or the resultant force. ➢ The resultant force is the vector sum of all the forces acting on an object.
- 17. ➢ Several forces can be combined or added to produce a single force- net force. ➢ A net force of zero indicates that all the forces cancel each other’s effect.
- 18. + = 1 2 3 + = = + 0 2 forces can combine so they add together(1), or subtract from each other (2). They may also cancel each other(3).
- 19. ➢ If no changes in the state of motion is produced, these forces are said to be BALANCED FORCE. ➢ If there is a net force, then this force is said to be the UNBALANCED FORCE.
- 20. Types of Forces ➢ Forces can be classified into two basic types based on how they are applied or how they act on the other objects. • Contact forces • Non-contact forces or action-at-a distance force.
- 21. Contact Forces 1. Applied Force 𝐹𝑎𝑝𝑝 - force applied to an object by another object or person. - the direction of the force applied depends on how the force is applied.
- 22. 2. Normal Force (N) - support force exerted upon an object that is in contact with another object. - referred as pressing force. - always directed toward the pressing object and acts perpendicularly to the surface of the object.
- 23. 3. Frictional Force (f) - force exerted by the surfaces in contact with each other and move relatively being pressed with each other. - friction opposed the motion.
- 24. - results when two surfaces are pressed together closely, causing attractive intermolecular forces bet. The molecules of the 2 diff. surfaces. -can be calculated using equation : f=μN, where μ is the coefficient of friction and N is the normal force.
- 25. 4. Air Resistance Force (Fair) - is a special type of frictional force that acts on objects as they travel through the air. - always opposes the motion of the moving object. - it is most noticeable in objects that travel at high speed or in objects with large surface areas.
- 27. 5. Tensional Force (T) - is the force which is transmitted through a string, rope, or wire when it is pulled tight by forces acting at each end.
- 28. 6. Spring Force (𝐹𝑠𝑝𝑟𝑖𝑛𝑔) - force exerted by a compressed or stretched spring on any object that is attached to the spring.
- 29. Non- Contact Forces 1. Force of Gravity (also Known as Weight, W) - force with which the Earth, moon, or massive body attracts an object toward itself.
- 30. - this is the weight of an object. - 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 and due to gravity which has a value of 9.8 m/s²( on Earth) and m is the object’s mass (in kg) .
- 31. 2. Electrical Force - this is the force that exist between charges. It can either be attractive or repulsive force. 3. Magnetic Force - this is the force that exist in magnets. It is the force that makes magnets attract or repel objects or other magnets.
- 32. Free-Body Diagram FBD - forces can be seen based on how they act 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).
- 33. When constructing FBD’s, the following assumptions are made: 1. Pulleys are assumed frictionless; 2. Pulleys are assumed weightless; 3. Ropes, cables, cords, and wires are assumed weightless.
- 34. In constructing FBD, one frees the body (or object) from its environment and draws the body indicating the magnitudes and direction of all forces acting on the body.