Force, Mass, and Acceleration PDF

Force, Mass, and Acceleration Objectives Analyze data to support the claim that Newton’s second law of motion describes the mathematical relationship among the net force on a macroscopic object, its mass, and its acceleration. Use Newton’s second law to predict changes in the motions of...

Force, Mass, and Acceleration Objectives Analyze data to support the claim that Newton’s second law of motion describes the mathematical relationship among the net force on a macroscopic object, its mass, and its acceleration. Use Newton’s second law to predict changes in the motions of objects. Force, Mass, and Acceleration If you push an object that is sitting on a table, what happens? It moves in the direction that it was pushed. If there are two objects sitting on the table, one more massive than the other, what happens if you push the same amount on each? The less massive object moves more than the more massive object. TYPES OF FORCES Gravitational Force: Did you know that the gravitation Electromagnetic Force: This force acts between char Nuclear Forces: These are the strongest forces in nat Inertia: According to Newton's First Law, an object at r Newton’s Third Law: For every action, there is an equ Friction: This force opposes the motion of objects. Th Centripetal Force: This force keeps objects moving in Buoyant Force: According to Archimedes’ principle, th Tension Force: This force is transmitted through a str Applied Force: Any force that is applied to an object b FORCES Changing Motion Newton’s first law of motion: Objects remain at rest or continue with uniform motion in a straight line unless some action causes a change in motion. Changing Motion What causes the change in the soccer ball’s motion? How does the velocity of the soccer ball change? The goalie’s hands cause the change in the soccer ball’s motion. The ball changes direction from toward the goalie to away from the goalie after she pushes it. Sailing stones also known as sliding rocks, are part of a geological phenomenon where rocks move and inscribe long tracks along a smooth valley floor without animal intervention. The movement of the rocks occurs when large, thin sheets of ice floating on an ephemeral winter pond are driven by light winds, pushing the rocks and leaving behind their tracks  Wind moves sailing stones, which glide along a thin layer of ice late at night. The acceleration is an effect Inertia Inertia: an object’s resistance to a change in motion Mass: a measure of the inertia of an object A B Inertia What are some differences between image A and image B? What do you notice about the motion of the boats? A B Inertia There are two people in Boat B and only one person in Boat A. The first boat has longer arrows for velocity and acceleration, which means that it is going faster and is speeding up more quickly. A B Inertia How can you explain the differences in images A and B using the terms “inertia” and “mass”? A B Inertia Boat A has less mass than boat B, therefore boat A has less inertia and is easier to accelerate. The acceleration of an object is inversely proportional to its mass. A B Law of Inertia The first law of motion states that objects at _____ stay at rest, and objects in _____ stay in motion unless acted upon by a _____. It would hurt just as much to kick a bowling ball on the moon as it would on Earth, because the ball’s properties, including its mass and inertia, would not be different on the moon.  Sketches should indicate smaller spaces between each pair of points due to the larger mass of the hovercraft and its occupants. What is the main idea of Newton's first law of motion, also known as the law of inertia? A) Objects at rest will always remain at rest, and objects in motion will always remain in motion. B) Objects in motion will slow down and eventually stop due to friction. C) Objects at rest will stay at rest, and objects in motion will stay in motion at a constant speed and direction unless acted upon by a net external force. D) Objects in motion will change their direction unless acted upon by a net external force. Force Causes an Acceleration A force is the cause of a change in motion or shape. Net force: the vector sum of all the forces acting on an object Newton’s second law of motion: the mathematical relationship between the net force and the change in motion Force Causes an Acceleration How can Newton’s second law of motion explain what is occurring in the image? The more force that is applied to push the chair causes the chair to accelerate faster, assuming that the mass of the two chairs is the same.)  Force is the independent variable. Changing the force affects the acceleration, which is the dependent variable. The force is the cause and the acceleration is the effect. The spaceship with the smaller mass would have the greater acceleration. Law of Acceleration The second law of motion states that the _____ acting on an object is equal to its _____ times its _____. This means that the more massive an object is, the harder it is to _____. It also means that the greater the _____ applied to an object, the greater its _____ will be. a = 0.84 m/s2 m = 0.45 kg What is the relationship between force, mass, and acceleration as described by Newton's second law ofA)motion? Force is directly proportional to mass and inversely proportional to acceleration. B) Force is equal to the mass of an object multiplied by its acceleration. C) Force is inversely proportional to mass and directly proportional to acceleration. D) Force is independent of mass and acceleration. I Push You, and You Push Back Newton’s third law of motion: The interaction between two objects can be represented as two forces having equal magnitudes and opposite directions. I Push You, and You Push Back What are the pairs of interacting forces in the image? (Between the person and the crate, between the person and the floor, and between the crate and the floor) I Push You, and You Push Back Between the person and the crate between the person and the floor, and between the crate and the floor I Push You, and You Push Back If one object in a third-law pair is much more massive than the other, what happens when they push away from each other? The less massive object will accelerate faster in one direction than the more massive object in the opposite direction. Law of Interaction (third-law pair) The third law of motion states that for every _____, there is an _____ and _____ reaction. It also explains that forces always come in _____. Sketches should show a hand petting a dog, with an arrow indicating a downward force from hand to dog, labeled FHD. An arrow in the opposite direction from the dog to the hand should be labeled FDH. Both arrows should be the same length to indicate that the hand pushes against the dog with the same force that the dog exerts on the hand. When we want to know the magnitude of a force that is needed to change the motion of an object, we need to know two things: ›The mass of the object. ›How much velocity of that object changed?  A body travelling at 100m/s is harder to stop than the same body travelling at 10m/s. If two bodies were travelling at the same speed the heavier one would be much harder to stop. The combination of the bodies velocity and mass seem to affect how difficult it is to stop. This combination is called Momentum. Momentum Newton’s second law of motion can be described in terms of the change in momentum over time. Momentum On a momentum vs. time graph, the slope gives the net force. Momentum The dot diagrams and the slope of the graph changes with different forces. Momentum Momentum: the product of the mass and velocity of an object Representing Forces System: whatever pieces of the universe you are interested in studying Free-body diagram: a graphical representation of all the forces and resulting effects on an object or system Representing Forces What is the system represented in the image? Representing Forces What forces are in the positive direction? What forces are in the negative direction? Positive forces are the force of the ground on the foot, the hand on the cart, the cart on the ground, and the cart on the books. Negative forces are the force of the foot on the ground, the cart on the hand, the ground on the cart, and the books on the cart. Representing Forces What forces are external to the system and affect the net force on the system? The force of the hand on the cart, and the force of the ground on the cart because they are the only forces that act on the system that are also paired with a force acting outside of the system  Ben (B) is pushing against Adam (A) (FBA) in the positive direction, as is Dana (D) (FDA). Carly (C) is pushing against Adam (A) in the opposite direction (FCA).  Sketches should show a longer vector arrow pointing in the positive direction and a shorter vector arrow pointing in the opposite (negative) direction. The magnitude of the resultant force on the object is 8 N in the positive direction. Modeling Force Statics: the study of balanced forces on objects or systems that are at rest Dynamics: the study of the forces on objects or systems that are in motion Force-acceleration equations: ΣF = 0 ΣF = ma 1Graphs should feature a straight line indicating momentum over time and unchanging velocity. Claims should indicate that the net force on the moving object can be zero if the object has no acceleration. The object has momentum, but it is not changing speed or direction, and therefore the net force acting on the object is zero