Chapter 6 Forces in Motion

Acceleration due to Gravity: ________________________________________ _______________________________________________________________ Objects accelerate towards earth at a ________________ rate of acceleration equal to _____________. For every ________________ an object is falling, its downward velocity increases by ________________. Objects fall to the ground at the same rate because the acceleration due to gravity is the same for all objects Which would fall faster off a cliff, Wile E. Coyote or a boulder? constant 9.8 m/s/ssecond 9.8 m/s Why does a sheet of paper fall more slowly than the same sheet of paper crumpled into a ball? _____________________________ air resistance Air (a _________) is also a ____________, so an object falling through it would be affected by ___________ ______________ opposing its motion. This is called _______ ___________________. A flat piece of paper has more air resistance than a crumpled piece of paper. gasfluid fluid friction air resistance

Terminal Velocity: Because the air resistance _______________ as an object’s speed _________________, eventually the _______________ force of air resistance will equal the __________________ force of gravity and the acceleration will be ___________. The object will then fall at _______________ velocity, which is called _______________ _______________. increases upward downward zeroconstant terminal velocity Free fall: An object is in free fall only if _________________ is the only force acting on it. This can only occur in a _________________ (where there is no air resistance). gravity vacuum Orbiting: An object is orbiting when it is traveling in a _______________ path around another object. It is moving by the combination of ___ motions: it is moving _____________ at constant ___________ and also ___________ ______________ because of __________________ pulling it toward the object at the center of the ____________. These two motions cause the path the object travels to be _______________. The unbalanced force that causes objects to move in a circular path is called a __________________ force, provided by ________________. circular 2 forwardspeedfree falling gravity orbit curved centripetal gravity Projectile motion: the ______________ path an object follows when thrown or propelled near the ______________ ____ _____ _____________. This is a combination of the ________________ (__________________) motion which is _________________ combined with the ________________ velocity because __________________ accelerates it ____________________. curved surface of the Earth forward horizontal constantvertical gravitydownward

Which will fall faster from the top of a tall building, an elephant or a feather? Option 1: ___________________________________ ___________________________________________ Option 2: ___________________________________ ___________________________________________ Option 3: ___________________________________ ___________________________________________ Scenario 1: This happens in air. Therefore we must consider ____________________. This depends on 1. __________________________________ 2. __________________________________ They will land at the same time because acceleration due to gravity is the same for all objects. The elephant will land first because it has a larger mass. The feather will land first because it has less air resistance. air resistance the speed of the falling object the surface area of the falling object

Which would have the greater surface area, the elephant or the feather? _____________________ So which should land first? __________________ But air resistance also depends on the _____________ at which the object falls. The faster it falls, the greater the __________________ it encounters. An object will continue to __________________ as it falls until the upward force of ____________________ equals the downward force of ________________. After that, the object will fall at a constant speed, called ___________ _________. The feather reaches the speed where _______________ equals the force of ________________ much sooner (and at a slower speed) than the elephant, so its terminal velocity is much less and it falls to earth more slowly. The elephant has a greater __________ and therefore a greater force due to gravity, and must reach a higher speed before air resistance pushing up can balance the force of gravity pulling down. Actually, it never reaches this point, so it never reaches _____________________. It continues to________________ for the entire fall. the elephant the feather? speed air resistance accelerate air resistance gravity terminal velocity air resistance gravity mass terminal velocityaccelerate

Conclusion for falling in air: The _____________ falls faster than the ______________ because it never reaches a ___________ ____________, but continues to _______________ as it falls. The feather reaches terminal velocity very early in its fall, so the remainder of its fall will occur with a __________ _____________. elephant featherterminal velocity accelerate slower velocity

Newton’s Laws of Motion Newton’s First Law of Motion: An object at _________ remains at __________ and an object in _____________ remains in ______________ at constant _______________ and in a ________________ ____________ unless acted on by an ___________________ force. rest motion speedstraight line unbalanced Question: If you are sitting still in your seat on a bus that is traveling 100 km/h on a highway, is your body at rest or in motion?________________________ What force usually stops an object from remaining in motion? ______________ in motion friction Inertia: the _______________ of all objects to ____________ any change in motion. The more _________ an object has, the more _______________ it has. tendency resist massinertia Newton’s Second Law of Motion: The ____________________ of an object depends on the ___________ of the object and the amount of _____________ applied. For the same force, an object’s acceleration ________________ as its mass _______________ and its acceleration ________________ as its mass ________________. For constant mass, an object’s acceleration ___________ as the force on it _________________, and its acceleration ______________ as the force on it _________________. acceleration massforce increases decreases increases decreases

Newton’s Second Law of Motion – mathematical formula: a = _______ F m acceleration = _______________Force mass Algebraically, this formula can be rearranged to solve for each of the 3 variables: F = m = maF a Example: If you hit an object of unknown mass with a force of 15 N, and the object then accelerates at 5 m/s/s, what is the mass of the object? ________ 3 kg Example: Calculate the force of gravity acting on your 6 kg backpack. (This is the weight of your backpack.) F = ma = 6 kg x 9.8 m/s/s = 58.8 N Example: A 50 g skater pushes off from a wall with a force of 200N. What is the skater’s acceleration? a = F/m = 200 N/50 g = 4 m/s/s

Newton’s Third Law of Motion: Whenever one object exerts a ___________ on a second object, the second object exerts an _____________ and __________________ force on the first object. force equal opposite All forces act in ___________, one force pushing one way, and another force pushing in the ________________ direction. This happens whether there is motion or no motion. Examples of opposite force pairs: A student sitting on a chair. The________ arrow shows the force of the student’s body pushing on the chair, and the ______________ arrow shows the force of the chair pushing up on the student. Since the forces are __________, there is no motion. pairs opposite red yellow equal When a hunter shoots a ____________ from his gun, the gun powder explosion pushes the bullet _______________, exerting a backwards force into the _______, which causes the gun to push back into the hunter’s _____________, which is exerting another force on the ________. bullet forward gun shoulder gun

Momentum: a _______________ of a moving object that depends on the object’s _____________ and __________________. The more momentum an object has, the ________________ it is to __________ it or change its ___________________. Conservation of Momentum: Any time two or more objects interact, they may _________________ momentum, but the total amount of ________________ stays the same. Example: playing _____________. When the cue ball hits another ball which is stationary, the cue ball ___________ or ________________ and the other ball starts ________________. property massvelocity harderstop direction exchange momentum pool stopsslows down The equation for momentum (p) is p =. What is the momentum of an 80 kg basketball player driving to the basket with a constant velocity of 8 m/s? m x v p = m x v = 80 kg x 8 m/s = 640 kg. m/s moving

Conservation of Momentum can be explained by Newton’s __________ _______. In the example of the pool balls, the cue ball hit the other ball with a certain amount of ____________, which was the __________ force. The _____________ force was the ___________ but _____________ force exerted on the cue ball by the pool ball. The ___________ force made the pool ball start _______________ and the ________________ force made the cue ball ______________. Third Law forceactionreaction equalopposite action moving reactionstop How does Newton’s second law explain why it is easier to push a bicycle than to push a car with the same acceleration? The bicycle has a smaller mass, so a smaller force is required to give it the same acceleration as the car. What are two ways that you can increase the acceleration of a loaded grocery cart? You can increase the force applied to the cart, or you can decrease the mass of the cart by removing some of the objects from it. How does Newton’s third law explain how a rocket takes off? The hot gases expelled from the back of the rocket produce a reaction force on the rocket that lifts and accelerates the rocket.

In the case of no air (or air resistance), will the elephant or the feather reach the ground first? The only force acting on the objects is the force of ____________. The force the elephant experiences is much ___________ than the force the feather experiences, so the elephant should experience greater acceleration. But according to Newton’s First Law of Motion, the _________ of an object resists _______________. Therefore, the greater __________ of the elephant (which tends to produce __________ acceleration) offsets the influence of the greater _____________. It is the __________________ ratio which determines the ___________________. = a = g gravity greater mass accelerationmass small forceforce/mass acceleration All objects (regardless of their mass) experience the same __________________ when in a state of free fall. When the only force is _________, the acceleration is the _________ value for all objects. acceleration gravity same

Chapter 6 Forces in Motion

Acceleration due to Gravity: ________________________________________ _______________________________________________________________ Objects accelerate towards earth at a ________________ rate of acceleration equal to _____________. For every ________________ an object is falling, its downward velocity increases by ________________. Which would fall faster off a cliff, Wile E. Coyote or a boulder? Why does a sheet of paper fall more slowly than the same sheet of paper crumpled into a ball? _____________________________ Air (a _________) is also a ____________, so an object falling through it would be affected by ___________ ______________ opposing its motion. This is called _______ ___________________. A flat piece of paper has more air resistance than a crumpled piece of paper.

Terminal Velocity: Because the air resistance _______________ as an object’s speed _________________, eventually the _______________ force of air resistance will equal the __________________ force of gravity and the acceleration will be ___________. The object will then fall at _______________ velocity, which is called _______________ _______________. Free fall: An object is in free fall only if _________________ is the only force acting on it. This can only occur in a _________________ (where there is no air resistance). Orbiting: An object is orbiting when it is traveling in a _______________ path around another object. It is moving by the combination of ___ motions: it is moving _____________ at constant ___________ and also ___________ ______________ because of __________________ pulling it toward the object at the center of the ____________. These two motions cause the path the object travels to be _______________. The unbalanced force that causes objects to move in a circular path is called a __________________ force, provided by ________________. Projectile motion: the ______________ path an object follows when thrown or propelled near the ______________ ____ _____ _____________. This is a combination of the ________________ (__________________) motion which is _________________ combined with the ________________ velocity because __________________ accelerates it ____________________.

Which will fall faster from the top of a tall building, an elephant or a feather? Option 1: ___________________________________ ___________________________________________ Option 2: ___________________________________ ___________________________________________ Option 3: ___________________________________ ___________________________________________ Scenario 1: This happens in air. Therefore we must consider ____________________. This depends on 1. __________________________________ 2. __________________________________

Which would have the greater surface area, the elephant or the feather? _____________________ So which should land first? __________________ But air resistance also depends on the _____________ at which the object falls. The faster it falls, the greater the __________________ it encounters. An object will continue to __________________ as it falls until the upward force of ____________________ equals the downward force of ________________. After that, the object will fall at a constant speed, called ___________ _________. The feather reaches the speed where _______________ equals the force of ________________ much sooner (and at a slower speed) than the elephant, so its terminal velocity is much less and it falls to earth more slowly. The elephant has a greater __________ and therefore a greater force due to gravity, and must reach a higher speed before air resistance pushing up can balance the force of gravity pulling down. Actually, it never reaches this point, so it never reaches _____________________. It continues to________________ for the entire fall.

Conclusion for falling in air: The _____________ falls faster than the ______________ because it never reaches a ___________ ____________, but continues to _______________ as it falls. The feather reaches terminal velocity very early in its fall, so the remainder of its fall will occur with a __________ _____________. elephant featherterminal velocity accelerate slower velocity

Newton’s Laws of Motion Newton’s First Law of Motion: An object at _________ remains at __________ and an object in _____________ remains in ______________ at constant _______________ and in a ________________ ____________ unless acted on by an ___________________ force. Question: If you are sitting still in your seat on a bus that is traveling 100 km/h on a highway, is your body at rest or in motion?________________________ What force usually stops an object from remaining in motion? ______________ Inertia: the _______________ of all objects to ____________ any change in motion. The more _________ an object has, the more _______________ it has. Newton’s Second Law of Motion: The ____________________ of an object depends on the ___________ of the object and the amount of _____________ applied. For the same force, an object’s acceleration ________________ as its mass _______________ and its acceleration ________________ as its mass ________________. For constant mass, an object’s acceleration ___________ as the force on it _________________, and its acceleration ______________ as the force on it _________________.

Newton’s Second Law of Motion – mathematical formula: a = _______ acceleration = _______________ Algebraically, this formula can be rearranged to solve for each of the 3 variables: F = m = Example: If you hit an object of unknown mass with a force of 15 N, and the object then accelerates at 5 m/s/s, what is the mass of the object? ________ Example: Calculate the force of gravity acting on your 6 kg backpack. (This is the weight of your backpack.) Example: A 50 g skater pushes off from a wall with a force of 200N. What is the skater’s acceleration?

Newton’s Third Law of Motion: Whenever one object exerts a ___________ on a second object, the second object exerts an _____________ and __________________ force on the first object. All forces act in ___________, one force pushing one way, and another force pushing in the ________________ direction. This happens whether there is motion or no motion. Examples of opposite force pairs: A student sitting on a chair. The________ arrow shows the force of the student’s body pushing on the chair, and the ______________ arrow shows the force of the chair pushing up on the student. Since the forces are __________, there is no motion. When a hunter shoots a ____________ from his gun, the gun powder explosion pushes the bullet _______________, exerting a backwards force into the _______, which causes the gun to push back into the hunter’s _____________, which is exerting another force on the ________.

Momentum: a _______________ of a moving object that depends on the object’s _____________ and __________________. The more momentum an object has, the ________________ it is to __________ it or change its ___________________. Conservation of Momentum: Any time two or more objects interact, they may _________________ momentum, but the total amount of ________________ stays the same. Example: playing _____________. When the cue ball hits another ball which is stationary, the cue ball ___________ or ________________ and the other ball starts ________________. The equation for momentum (p) is p =. What is the momentum of an 80 kg basketball player driving to the basket with a constant velocity of 8 m/s?

Conservation of Momentum can be explained by Newton’s __________ _______. In the example of the pool balls, the cue ball hit the other ball with a certain amount of ____________, which was the __________ force. The _____________ force was the ___________ but _____________ force exerted on the cue ball by the pool ball. The ___________ force made the pool ball start _______________ and the ________________ force made the cue ball ______________. How does Newton’s second law explain why it is easier to push a bicycle than to push a car with the same acceleration? What are two ways that you can increase the acceleration of a loaded grocery cart? How does Newton’s third law explain how a rocket takes off?

In the case of no air (or air resistance), will the elephant or the feather reach the ground first? The only force acting on the objects is the force of ____________. The force the elephant experiences is much ___________ than the force the feather experiences, so the elephant should experience greater acceleration. But according to Newton’s First Law of Motion, the _________ of an object resists _______________. Therefore, the greater __________ of the elephant (which tends to produce __________ acceleration) offsets the influence of the greater _____________. It is the __________________ ratio which determines the ___________________. = a = g All objects (regardless of their mass) experience the same __________________ when in a state of free fall. When the only force is _________, the acceleration is the _________ value for all objects.