Ch4_BarinskyL

toc **¡Chapter 4!**

Lesson 1 a-d, Method 4
11/14/11

1) What is Newton's first law? -//This is the law of inertia, saying that an object at rest stays at rest and an object in motion stays in motion with the same speed and direction unless acted upon by an unbalanced force.// 2) How is the first law applied in everyday situations? -//All motion (or lack thereof) has to do with inertia. When we walk, our feet would slide out from under us if friction didn't act upon them and keep them from moving.// 3) What actually is inertia? //-Inertia is the// //resistance an object has to a change in its state of motion.// 4) What did Galileo discover? //-He found that friction was the reason a ball on an incline does not reach its original height on its way back up an opposite incline. He said that the ball would reach the height eventually if friction could be eliminated.// 5) Do forces only keep objects in motion? //-Forces can bring objects to a rest. For example, a book sliding on a table will stop because of the friction acting in the opposite way.// 6) What does an object's mass have to do with inertia? //-The object's ability to resist changes in its state of motion varies with mass. Mass is solely dependent on the inertia of an object.// //The more inertia that an object has, the more mass that it has. A more massive object has a greater tendency to resist changes in its state of motion.// 7) What actually is an object's state of motion? -//It is define by its velocity (its speed with a direction).// 8) Can the definition of inertia be worded any differently? //-Inertia is the tendency of an object to resist changes in its velocity (state of motion). Therefore, it is also the tendency of an object to resist accelerations.// 9) What is an unbalanced force? //-An object is being acting upon unbalanced forces when the forces are not of same magnitude and are not acting in opposite directions. Unbalanced forces cause acceleration, and therefore, a change in the object's state of motion.// 10) When is there equilibrium in a system? //-There is equilibrium when the forces acting on an object are of the same magnitude and are acting in opposite directions, causing no change in its state of motion.//

Lesson 2 a-d, Method 4
11/15/11

1) What is a force? //-A force is a push or a pull on// //an object resulting from the object's// //interaction// //with another object//. 2) What is the difference between a contact force and an action-at-a-distance force? -//A contact forces occur between objects when the objects are physically touching. Action-at-a-distance forces occur when the objects are not in physical contact with each other.// 3) What are examples of the two types of force? //-Contact forces: Friction, tension, normal force, air resistance, applied force, spring. Action-at-a-distance: Gravity, electricity, magnetism// 4) What are the 7 types of force? //-The forces are: applied force, gravity (weight), normal force, friction, air resistance, tension, and spring force.// 5) What is the difference between mass and weight? //-Weight is the force of gravity acting on an object. Mass is the amount of matter contained in an object.// 6) What is the difference between sliding friction and static friction? //-Sliding friction occurs// //when an object slides across// //a surface. Static friction occurs when the surfaces of two objects are at rest relative to one another and a force exists// //on one of the objects to set it into motion relative to the other object.// 7) What is a free-body diagram? -//They are diagrams used to show the relative magnitude and direction of all forces// //acting upon an object in a given situation. (example on right)// 8) What is a net force? -//It is the vector sum of all the forces that act upon an object//. 9) If there is a net force, what happens? -//There will be an acceleration on the object because the forces are unbalanced.//

Lesson 3 a-b, Method 4
11/16/11

1) What is Newton's second law? -//The acceleration of an object as produced by a net force is directly proportional to the magnitude of the net force, in the same direction as the net force, and inversely proportional to the mass of the object (Net Force = m * a).// //2)// What does the law basically say? //-////The acceleration of an object is dependent on the net force acting on the object and the mass of the object. As the force acting upon an object is increased, the acceleration of the object is increased. As the mass of an object is increased, the acceleration of the object is decreased.// 3) How is the first law different from the second? -//The first law predicts the behavior of objects for which all existing forces are balanced, while the second law pertains to the behavior of objects for which all existing forces are unbalanced.// 4) What is the big misconception about Newton's laws? -//Many people do not fully understand or believe the laws because of the ideas about physics that they already had in their heads and are unwilling to give up.//