Section 1: Gravity and motion
vocabulary
1) Terminal Velocity: the constant velocity of a falling object when the force of air resistance is equal in magnitude and opposite in direction to the force of gravity
2) Free Fall: the motion of a body when only the force of gravity is acting on the body
3) Projectile Motion: the curved path that an object follows when thrown, launched, or otherwise projected near the surface of Earth
2) Free Fall: the motion of a body when only the force of gravity is acting on the body
3) Projectile Motion: the curved path that an object follows when thrown, launched, or otherwise projected near the surface of Earth
section summary
This section discussed gravity and motion. For a very long time people believed that the more mass an object has, the faster it falls to the ground, but this was dis-proven by Italian scientist Galileo Galilei who proved that objects fall to the ground at the same rate (9.8 m/s squared) because acceleration due to gravity is the same for all objects (besides while in a vacuum). Also, acceleration is the rate at which velocity changes, and velocity of falling objects can be found by the equation change in velocity (delta "v") is equal to the acceleration due to gravity on Earth multiplied by time in takes to fall [in seconds] (= g x t).
Air resistance is another force that opposes motion of objects through the air. The amount of air resistance acting on an object depends on the objects size, shape, and speed of the objects (Ex: Air resistance acts more on a flat sheet of paper than a crumpled up piece due to a larger surface area). Terminal velocity and free fall are also related to air resistance. Terminal velocity (vocabulary word 1) is the constant velocity of a falling object when the force of air resistance is equal in magnitude and opposite in direction to the force of gravity. In other words, terminal velocity is the velocity of objects with all of the forces acting on it applied. However, when there are no other forces acting on an object besides gravity, this is called free fall (vocabulary word 2). Orbiting (the path of the object + centripetal force) objects are in continuous free fall because they are constantly falling away from an object at the same rate that they are attracted to it. Next, is projectile motion (vocabulary word 3), which is the curved path an object follows when it is thrown or propelled near the surface of the Earth. Projectile motion is composed of two parts, horizontal motion and vertical motion, which have no effect on each other. However, when the two are combined, they form a curved path. In horizontal motion, you may exert a force on an object that makes it go forward, that forward motion is horizontal motion, which is parallel to the ground. So after you apply force to an object (lets say a Frisbee) on horizontal forces are acting on the Frisbee, so there are no horizontal fores to change the Frisbee's horizontal motion (the horizontal velocity is constant). Vertical motion however, is motion that is perpendicular to the ground (which on Earth is caused by the Earth's gravity). So, without horizontal motion, an object that you apply force to would just fall straight down to the Earth, and without vertical motion the object would continue moving forward forever (theoretically if if don't apply air resistance and other various forces). However (as stated earlier), when the two parts of projectile motion (Horizontal & Vertical) are put together they cause the curved path an object takes when projected near Earth's surface.
Air resistance is another force that opposes motion of objects through the air. The amount of air resistance acting on an object depends on the objects size, shape, and speed of the objects (Ex: Air resistance acts more on a flat sheet of paper than a crumpled up piece due to a larger surface area). Terminal velocity and free fall are also related to air resistance. Terminal velocity (vocabulary word 1) is the constant velocity of a falling object when the force of air resistance is equal in magnitude and opposite in direction to the force of gravity. In other words, terminal velocity is the velocity of objects with all of the forces acting on it applied. However, when there are no other forces acting on an object besides gravity, this is called free fall (vocabulary word 2). Orbiting (the path of the object + centripetal force) objects are in continuous free fall because they are constantly falling away from an object at the same rate that they are attracted to it. Next, is projectile motion (vocabulary word 3), which is the curved path an object follows when it is thrown or propelled near the surface of the Earth. Projectile motion is composed of two parts, horizontal motion and vertical motion, which have no effect on each other. However, when the two are combined, they form a curved path. In horizontal motion, you may exert a force on an object that makes it go forward, that forward motion is horizontal motion, which is parallel to the ground. So after you apply force to an object (lets say a Frisbee) on horizontal forces are acting on the Frisbee, so there are no horizontal fores to change the Frisbee's horizontal motion (the horizontal velocity is constant). Vertical motion however, is motion that is perpendicular to the ground (which on Earth is caused by the Earth's gravity). So, without horizontal motion, an object that you apply force to would just fall straight down to the Earth, and without vertical motion the object would continue moving forward forever (theoretically if if don't apply air resistance and other various forces). However (as stated earlier), when the two parts of projectile motion (Horizontal & Vertical) are put together they cause the curved path an object takes when projected near Earth's surface.
SectioN 2: Newton's laws of motion
vocabulary
1) Inertia: the tendency of an object to resist being moved or, if the object is moving, to resist a change in speed or direction until an outside force acts on the object
section summary
This section discussed newton's laws of motion. Newton's first law of motion states that an object at rest (not moving) remains at rest, and an object in motion remains in motion at a constant speed and in a straight line unless acted on by an unbalanced force. This law describes the motion of an object with a net force of 0 N acting on it. For example, any moving object will not stop moving or slow down unless a force is exerted on it, and a non-moving object will not begin moving unless a force is exerted on it. Friction may also sometimes cause the observation of Newton's first law to become difficult because friction may cause an object to move more slowly than it would without friction.Friction is also a reason why moving objects eventually stop moving. Newton's first law is also sometimes referred to as the law of inertia, because inertia (vocabulary word 1) is the tendency of all objects to resist any change in motion. The inertia of an object depends on its mass (mass is a measure of inertia). The greater the mass of an object, the greater it's inertia is, which means that the greater the mass of an object is, the harder it is to change the motion of that object (Ex: It's easier to change the motion of a shopping cart than it is a car). Likewise, inertia is the reason a moving object stays in motion with the same velocity unless a force changes its speed or direction.
Next, is Newton's second law of motion, which states that the acceleration of an object depends on the mass of the object and the amount of force applied. In other words, the greater the mass of an object, the more force is needed to be applied for it to accelerate as much as a smaller object. So, less force is needed to be exerted on a less massive object to get it to go a certain distance than is needed to be exerted on a more massive object to get it to go the same distance. This law can be expressed mathematically as either a=F/m (acceleration is equal to force divided by mass) or F=m x a (Force is equal to mass multiplied by acceleration). Newton's second law explains why objects fall to Earth with the same acceleration.
Lastly, is Newton's third law of motion, which states that whenever one object exerts a force on a second object, the second object exerts an equal and opposite force on the first (all forces act in pairs that are equal in size & opposite in direction). This law is true for all forces, including action and reaction forces, however, action and reaction forces do not act on the same object. For example, if a person is running, the action force is the persons foot pushing down on the ground, and the reaction force is the ground pushing up on the persons foot. The reaction force is what causes the runner to move forward. As simple as action forces may be, reaction forces are often difficult to see. For example, if you drop a ball, gravity pulls the ball towards (the action force), but the reaction force is the ball pulling the Earth towards itself. This may be hard to notice because the gravitational force of the ball is so weak in comparison to the Earth's own (due to each of their masses, with the Earth's mass being much greater).
Next, is Newton's second law of motion, which states that the acceleration of an object depends on the mass of the object and the amount of force applied. In other words, the greater the mass of an object, the more force is needed to be applied for it to accelerate as much as a smaller object. So, less force is needed to be exerted on a less massive object to get it to go a certain distance than is needed to be exerted on a more massive object to get it to go the same distance. This law can be expressed mathematically as either a=F/m (acceleration is equal to force divided by mass) or F=m x a (Force is equal to mass multiplied by acceleration). Newton's second law explains why objects fall to Earth with the same acceleration.
Lastly, is Newton's third law of motion, which states that whenever one object exerts a force on a second object, the second object exerts an equal and opposite force on the first (all forces act in pairs that are equal in size & opposite in direction). This law is true for all forces, including action and reaction forces, however, action and reaction forces do not act on the same object. For example, if a person is running, the action force is the persons foot pushing down on the ground, and the reaction force is the ground pushing up on the persons foot. The reaction force is what causes the runner to move forward. As simple as action forces may be, reaction forces are often difficult to see. For example, if you drop a ball, gravity pulls the ball towards (the action force), but the reaction force is the ball pulling the Earth towards itself. This may be hard to notice because the gravitational force of the ball is so weak in comparison to the Earth's own (due to each of their masses, with the Earth's mass being much greater).
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section 3: Momentum
vocabulary
1) Momentum: a quantity defined as the product of the mass and velocity of an object
section summary
This section discussed momentum (vocabulary word 1), which is a quantity defined as the product of the mass and velocity of an object. Momentum can be calculated using the equation p=m x v (momentum is equal to mass multiplied by velocity). The units of momentum are in kilograms multiplied by meters per second (kg x m/s) and always has a direction which is in the same direction as the objects velocity.Next, is the law of conservation of momentum, which states that any time objects collide, the total amount of momentum stays the same. This law applies whether the objects stick together or bounce off of each other upon collision, and only when there are no other forces acting on the colliding objects. For example, when one object hits another object, the momentum doesn't go away, it is simply transferred from one object to the other object. This can also be an example of Newtons third law because the first object hitting the second object is the action force, and the second object pushing back with the same force but in the opposite direction is the reaction force. Because action forces are equal and opposite, momentum is neither gained nor lost.Lastly, is when objects stick together or bounce off of each other upon collision. When objects stick together upon collision their masses become one whole mass, and the momentum is shared among all of the objects. In a head-in collision, the combined objects move in the direction of the object that had the greater momentum before the collision, but together the objects have different velocities that differs from the velocities of either object before the collision. When objects bounce off of each other, the
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