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- 1. Force and Newton's First Lawof Motion
- 2. OBJECTIVES At the endof this lesson, you will be able to: • differentiate contact and non-contact forces; • apply Newton’s 1st law to obtain quantitative and qualitative conclusions about the contact and non- contact forces acting on a body in equilibrium; • define inertial frames of reference; and • distinguish mass and weight. 2
- 3. 3 WHY DOES ITMOVE? “FORCE”
- 4. WHAT IS AFORCE? • is a push or pull of an object. • It is an interaction between two objects or between an object and its environment. • Force is a vector quantity, it has magnitude and direction. In most cases, it is denoted by the variable F.
- 5. WHAT IS THEUNIT OF FORCE? • Force is a quantity that is measured using the standard metric unit known as the Newton. • A Newton is denoted by the variable N and is equivalent to the product of a unit mass multiplied by a unit acceleration as shown:
- 6. FORCE SCALAR ORVECTOR? • force is a vector quantity. Therefore, a force has a magnitude and direction. • For forces which are directed towards the primary directions, their sign convention is: + positive when directed upwards or to the right. - negative when directed downwards or to the left.
- 7. FORCE SCALAR ORVECTOR? • forces with their magnitude and direction can also graphically as shown below:
- 8. NET FORCE ORRESULTANT FORCE 8 • is the sum of all the forces that act on the system Free body diagram
- 9. BALANCED VS UNBALANCEDFORCES • Balanced Forces forces acting on an object that do not cause change in the object's motions. (net force=0) • Unbalanced forces forces that cause a change in an object's motion
- 10. CONTACT AND NON-CONTACTFORCE • Contact Force - these are forces that involve physical contact between bodies • Non-contact Force or Action-at-a-distance Force - these are forces that do not involve physical contact between bodies
- 11. CONTACT AND NON-CONTACTFORCE Contact Force Non-contact Force Applied Force Gravitational Force (Weight) Normal Force Electrical Force Friction Force Magnetic Force Tension Force Spring Force Air/Fluid Resistance Force
- 12. Applied Force (Fapp) Appliedforce is the force applied to an object by a person or another object.
- 13. Normal Force (FNor N) The normal force is the support force or reaction force exerted upon an object that is in contact with another stable object. The normal force is always perpendicular to the surface.
- 14. Friction Force (Ff) Frictionoccurs when a surface resists the sliding of an object. It is always parallel to the surface and directed opposite of the motion.
- 15. Tension Force (Ftor T) Tension is a pulling force exerted on an object by a rope, string, cord, or chain. It is always a pull and never a push kind of force.
- 16. Air/Fluid Resistance Force(Fair/fluid) The air/fluid resistance is a special type of frictional force that acts upon objects as they travel through the air. This air resistance is sometimes called drag force and fluid resistance is sometimes called buoyant force.
- 17. Gravitational Force orWeight (Fgrav or W) The pull of gravity on an object and is also called weight. It is the force of gravity with which the earth, moon, or other massively large object attracts another object towards itself. Since the earth is round and the center is inside it, the direction of the weight is always downward.
- 18. Magnetic Force (Fmag) Themagnetic force is the attraction or repulsion that arises between electrically charged particles because of their motion. Magnetism is closely related to electricity.
- 19. ISAAC NEWTON’S LAWOF MOTION Sir Isaac Newton was a physicist and mathematician who developed the principles of modern physics, including the laws of motion and is credited as one of the great minds of the 17th-century Scientific Revolution.
- 20. ISAAC NEWTON’S LAWOF MOTION LAW #1: A body at rest will remain at rest, and a body in motion will remain in motion unless it is acted upon by an external force. LAW #2: The force acting on an object is equal to the mass of that object times its acceleration, F=ma LAW #3: For every action, there is an equal and opposite reaction.
- 21. 1ST LAW OFMOTION "A body at rest will remain at rest, and a body in motion will remain in motion, unless it is acted upon by an external force."
- 22. 1ST LAW OFMOTION (Law of Inertia) Inertia is the resistance an object has to a change in its state of motion. “The more inertia that an object has, the more mass that it has”
- 23. 1ST LAW OFMOTION (Law of Inertia) There are three types of Inertia following Newton's 1st Law: 1. Inertia of Rest 2. Inertia of Motion 3.Inertia of Direction
- 24. 1ST LAW OFMOTION (Law of Inertia) There are three types of Inertia following Newton's 1st Law: 1. Inertia of Rest 2. Inertia of Motion 3.Inertia of Direction
- 25. 1ST LAW OFMOTION (Law of Inertia) There are three types of Inertia following Newton's 1st Law: 1. Inertia of Rest 2. Inertia of Motion 3.Inertia of Direction
- 26. INERTIAL REFERENCE FRAME Inertialframe of reference is any frame in which an object remains either at rest or at a constant velocity unless another force acts upon it.
- 27. WEIGHT NOTE: g mayvaries on the location of the problem. acceleration due to the gravity of the EARTH is 9.8m/s2 or 32ft/s2 and the acceleration due to the gravity of the MOON is 1.6m/s2 or 5.3ft/s2
- 28. EXAMPLE 1 What isIvan's weight if he weighs 55 kg? If Ivan goes to the Moon (gmoon=1.6m/s2), what will be his new weight?