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Explore the concept of friction and inertia, and their role in the motion of objects. Discover how friction affects the need for a force to keep an object moving, and how mass influences inertia.
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GEORGIAPERFORMANCESTANDARDS SP1: Students will analyze the relationships between force, mass, gravity, and the motion of objects. d. Measure and calculate the magnitude of frictional forces and Newton’s three laws of motion.
Essential Question 3.3: ►Ultimately, what is the source of friction?
3.3 Galileo on Motion Galileo argued that only when friction is present –as it usually is– is a force necessary to keep an object moving.
3.3.1Friction: the force that acts between materials that touch as they move past each other.
3.3.2 Friction is caused by irregularities in the surfaces of objects that are touching.
3.3.3 If friction were absent, a moving object would neednoforce whatever to remain in motion.
When the ball rolls downward, it moves with Earth’s gravity, and its speed increases.
When the ball rolls upward, it moves against gravity and loses speed
When the ball rolls on a level plane, it does not move with or against gravity.
The ball rolling down the incline rolls up the opposite incline and reaches its initial height
As the angle of the upward incline is reduced, the ball rolls a greater distance before reaching its initial height.
If there is no friction, the ball will never stop unless it hits something.
3.3.4Galileo stated that the tendency of a moving body to keep moving is a natural tendency.
3.3.5 Every material object resists change to its state of motion.
3.3.6 The property of a body to resist changes to its state of motion is calledinertia.
According to Galileo, when is force needed to keep an object moving? CONCEPT CHECK Galileo argued that only when friction is present is a force needed to keep an object moving
Essential Question 3.4 : ►Is a constant force really necessary to keep an object moving?
3.4 Newton’s Law of Inertia Newton’s first law states that every object continues in a state of rest, or of uniform speed in a straight line, unless acted on by a nonzero net force.
3.4.1Objects in a state of rest tend to remain at rest. Only a force will change that state.
3.4.2In the absence of forces, a moving object tends to move in a straight line indefinitely.
3.4.3 A force is only needed to (1) overcome any friction that may be present and (2) to set objects into motion initially.
Essential Question 3.5 : ►Why is it commonly said that “inertia is a property of matter”?
3.5 Mass- A Measure of Inertia The more mass an object has, the greater its inertia and the more force it takes to change its state of motion.
3.5.1Mass is the quantity of matter in an object. Mass is a measure of the inertia in an object. You can tell how much matter is in a can when you kick it.
The standard kilogram is housed at the International Bureau of Weights and Standards near Paris.
3.5.3A large mass does NOT mean a large volume. The pillow has a larger size (volume) but a smaller mass than the battery.
3.5.4Weightis the force of gravity on an object. Weight depends on an object’s location – mass remains constant regardless of location (unless, of course, matter is removed or added.)
3.5.5Mass and weight are proportional to each other, but they are not equal to each other.
3.5.6Mass has to do with the amountofmatter in the object, while weight has to do with how strongly that matter is attracted by gravity.
3.5.7One kilogram weighs 10 newtons.The SI units of mass is the kilogram – about 2.2 pounds. The SI unit of force is thenewton (N).
One kilogram of nails weighs 10 N, which is equal to 2.2 pounds 10N
3.5.8 Weight = mass x gravity kg x m kg m s2 s2
