1. GALILEO AND INERTIA Galileo developed the first concept of laws of motion. Among these are the following: . the concept of motion in terms of velocity (speed and direction) by using inclined planes. . the idea of force that causes motion. . the natural state of an object is rest or uniformed motion. . the idea that objects resist motion, inertia. Galileo Galilei 1564-1642 Source : https://upload.wikimedia.org/wikipedia/commo ns/b/b0/Galileo-sustermans.jpg According to Galileo, objects in motion eventually stop because of a force called friction. Friction is a force that opposes motion between any surfaces that are touching. This is based on his experiment observed in inclined planes. He said that a difference between initial and final heights was due to the presence of friction. Galileo hypothesized that if friction could be entirely eliminated, the ball would reach exactly the same height. Or if the ball rolls horizontally and there's no friction that acts on it, the ball will never stop. If friction could be eliminated... Initial height Initial height equals equals final height final height with a steep angle As the angle of the opposing incline a ball will roll a is reduced, the bell must roll even small distance to a farther distance in order to attain attain the original the original height. What happens if height. the opposing incline is not inclined?If friction could be eliminated... If a ball stops when it attains its original height, then this ball would never stop. It would roll forever if friction were absent. II. ISAAC NEWTON AND HIS FIRST LAW OF MOTION Isaac Newton was born the same year Galileo died. He expanded Galileo's work and came up with his Three Laws of Motion. Newton's first law of motion, also known as Law of Inertia is based on Galileo's idea of inertia. Newton's Law of Inertia states that... An object at rest stays at rest and an object in motion stays in motion with the same speed and in the same direction unless acted upon by an unbalanced force. Isaac Newton 1642-1727 Source: INERTIA https://en.wikipedia.org/wiki/Isaac_Newton#/media/File: Portrait_of_Sir_Isaac Newton, 1689.jpg Inertia is the tendency of an object to resist change when in motion or when at rest. If an object is moving, inertia will keep it in motion. When it is at rest, it will continue to be at rest, unless there is a force applied on it. Three types of Inertia: . Inertia of rest - an object will stay in place unless something or somebody moves it. Example: a plate on the table Inertia of motion - an object will continue at the same speed until a force act on it. Example: a rolling ball Inertia of Direction - an object will stay moving in the same direction unless a force acts on it. Example: a moving car turning right MASS AND INERTIA An object's inertia depends on its mass. Mass is the amount of matter or substance that makes up an object. It is measured in units called kilogram. An object with a greater mass has a greater inertia and an object with a lesser mass will also have a lesser inertia. An object's tendency to resist change in its motion depends on its mass.FORCE Force causes an object to move, to stop or remain at rest. It is defined as a push or a pull. Newton (N) is the unit of force. One Newton is the amount of force required to give a 1- kg mass an acceleration of 1 m/s/s. Thus, the following unit equivalency can be stated as: 1 Newton = 1 kg . m/s" Friction Friction is a force that opposes motion between any surfaces that are touching. A rolling marble on the floor that suddenly stops when it reached a rough surface does not stop because of the absence of a force, It stops because of the presence of a force called friction. Friction occurs because no surface is perfectly smooth. Rough surfaces have more friction than smooth surfaces. Heavier objects also have more friction because they are pressed harder with greater force than lighter objects. Balanced and Unbalanced Forces A balanced force is a force in which the net force is equal to zero. A net force is the total combination of forces (in opposite direction or the same direction) acting on an object. Source shing //physics. schooluk.com/forces_and the interactionsheart Let's consider the free body diagram of a book on the table. There are two forces acting on the flower vase. The force of the table pushing the book upward also called the normal force and the gravitational force pushing the book downward. The forces on the book are balanced. Since the two forces are equal and in opposite directions, they balanced each other. The net force is zero, it means that the book is at its equilibrium. There is no unbalanced force acting on it thus it remains at rest. An unbalanced force is a force in which the net force is greater than zero. 400 N 300 NThe force produced by the left team is greater than the right team by 100N tipping the rope to the left direction. Unbalanced forces cause acceleration. Only unbalanced force can change the motion and direction of an object. LEARNING COMPETENCY WITH CODE: MELC: Explain the subtle distinction between Newton's 1st Law of Motion (or Law of Inertia) and Galileo's assertion that force is not necessary to sustain horizontal motion CG LC/ Code: ($11/12PS-IVd-51) ACTIVITIES/ EXERCISES: ACTIVITY 1: INERTIA! DIRECTIONS: Read and analyze the different situations given below. Identify the type of inertia in the given Situation. Select your answer from the box below. Inertia of direction Inertia of rest Inertia of motion 1. When pulling a Band-Aid off, it is better to pull it fast. Your skin will remain at rest due to inertia, and the force pulls the Band-Aid off. 2. When pedaling a bicycle and you stop pedaling, the bike continues going until friction or gravity slows it down. 3. When you stir coffee in a cup and stop, the swirling motion continues due to inertia. 4. If a car is moving forward it will continue to move forward unless friction or the brakes interfere with its movement. . 5. If the wind is blowing, tree branches are moving. Fruits that fall from the tree will fall in the direction the wind is moving into because of inertia. ACTIVITY 2: MASS VS. INERTIA! DIRECTIONS: Analyze the following picture and answer the guide questions that follows. A. Below is a wooden box and a Styrofoam box. wooden box styrofoam boxGuide Questions: 1. Which do you think has a greater mass? 2. Which has a greater inertia? Defend your answer. 3. Which will have a greater friction when move? Defend your answer. B. Study the picture below and answer the following question. Bryan and Alyss's Daniel and Maria Source: https:www.slid s-gr7 Guide Questions: 1. Whom do you think will win the game? Why? 2. What is the net force acting in the rope and in which direction is its motion? 3. Is it a balance or unbalance force? ACTIVITY 3: TRUE or FALSE DIRECTIONS: Write TRUE if the statement is correct otherwise write FALSE. 1. Friction is a force that opposes motion between any surfaces that are touching 2. difference between initial and final heights was due to the presence of friction. 3. An object with a greater mass has a greater inertia and an object with a lesser mass will also have a lesser inertia. 4. An object's tendency to resist change in its motion depends on its mass. Inertia is the tendency of an object to resist change when in motion or when at rest 6. Kilogram is the unit of Force. 7. A rolling marble on the floor that suddenly stops when it reached a rough surface does not stop because of the absence of a force, it stops because of the presence of a force called friction. 8. Smooth surfaces have more friction than rough surfaces. 9. Balance force has a net force of 0. 10. Only unbalanced force can change the motion and direction of an object. ACTIVITY 4: LAW OF MOTION! DIRECTIONS: Answer the following questions. 1. What is/are the contribution of Galileo in Newton's First law of motion? 2. What is Newton's law of inertia? 3. A ball is rolling across the top of a billiard table and slowly rolls to a stop. How would Galileo and Newton interpret the observation? 4. How does the law of inertia apply to object in motion