Unit 7: Motion & Forces
SPS8. Obtain, evaluate, and communicate information to explain the relationships among force, mass, and motion.
a. Plan and carry out an investigation and analyze the motion of an object using mathematical and graphical models. (Clarification statement: Mathematical and graphical models could include distance, displacement, speed, velocity, time, and acceleration.)
b. Construct an explanation based on experimental evidence to support the claims presented in Newton’s three laws of motion. (Clarification statement: Evidence could demonstrate relationships among force, mass, velocity, and acceleration.)
c. Analyze and interpret data to identify the relationship between mass and gravitational force for falling objects.
d. Use mathematics and computational thinking to identify the relationships between work, mechanical advantage, and simple machines.
a. Plan and carry out an investigation and analyze the motion of an object using mathematical and graphical models. (Clarification statement: Mathematical and graphical models could include distance, displacement, speed, velocity, time, and acceleration.)
b. Construct an explanation based on experimental evidence to support the claims presented in Newton’s three laws of motion. (Clarification statement: Evidence could demonstrate relationships among force, mass, velocity, and acceleration.)
c. Analyze and interpret data to identify the relationship between mass and gravitational force for falling objects.
d. Use mathematics and computational thinking to identify the relationships between work, mechanical advantage, and simple machines.
Reading Assignment: Book Chapters
Chapter 2: Motion
Sections 1, 2, & 3
Chapter 3: Forces
Sections 1, 2, & 3
Chapter 5: Work and Machines
Section 2
Sections 1, 2, & 3
Chapter 3: Forces
Sections 1, 2, & 3
Chapter 5: Work and Machines
Section 2
Formulas
During this unit, students will be using the following formulas to analyze and interpret mathematical and graphical models. Students will be allowed to use the Georgia Milestone Formula Sheet on all quizzes, test, and the Georgia Milestone Exam.
Speed, Velocity, & Acceleration
Motion in Sports
Click HERE to watch the Motion in Sports video. Georgia Tech's walk-off touchdown against Florida State University.
Forces in Motion Video
Forces and Motion PowerPoint
Phenomenia: Gravity
NASA: Scale in the Sky
The force of gravity not only keeps us from floating away, it lets NASA study Earth’s water and ice from space. Using a pair of twin satellites named GRACE, we can monitor where our planet’s water is going, even when it is underground. Watch the following video about the relationship between gravity and the water cycle.
The force of gravity not only keeps us from floating away, it lets NASA study Earth’s water and ice from space. Using a pair of twin satellites named GRACE, we can monitor where our planet’s water is going, even when it is underground. Watch the following video about the relationship between gravity and the water cycle.
Projectile Motion: Mythbusters
Phenomena: Seat belts & Newton's Laws
The Car and The Wall
According to Newton's first law, an object in motion continues in motion with the same speed and in the same direction unless acted upon by an unbalanced force. It is the natural tendency of objects to keep on doing what they're doing. All objects resist changes in their state of motion. In the absence of an unbalanced force, an object in motion will maintain its state of motion. This is often called the law of inertia.
The law of inertia is most commonly experienced when riding in cars and trucks. In fact, the tendency of moving objects to continue in motion is a common cause of a variety of transportation injuries - of both small and large magnitudes. Consider for instance the unfortunate collision of a car with a wall. Upon contact with the wall, an unbalanced force acts upon the car to abruptly decelerate it to rest. Any passengers in the car will also be decelerated to rest if they are strapped to the car by seat belts. Being strapped tightly to the car, the passengers share the same state of motion as the car. As the car accelerates, the passengers accelerate with it; as the car decelerates, the passengers decelerate with it; and as the car maintains a constant speed, the passengers maintain a constant speed as well.
But what would happen if the passengers were not wearing the seat belt? What motion would the passengers undergo if they failed to use their seat belts and the car were brought to a sudden and abrupt halt by a collision with a wall? Were this scenario to occur, the passengers would no longer share the same state of motion as the car. The use of the seat belt assures that the forces necessary for accelerated and decelerated motion exist. Yet, if the seat belt is not used, the passengers are more likely to maintain its state of motion.
Can you relate Newton's other 2 laws to this video? Explain.
According to Newton's first law, an object in motion continues in motion with the same speed and in the same direction unless acted upon by an unbalanced force. It is the natural tendency of objects to keep on doing what they're doing. All objects resist changes in their state of motion. In the absence of an unbalanced force, an object in motion will maintain its state of motion. This is often called the law of inertia.
The law of inertia is most commonly experienced when riding in cars and trucks. In fact, the tendency of moving objects to continue in motion is a common cause of a variety of transportation injuries - of both small and large magnitudes. Consider for instance the unfortunate collision of a car with a wall. Upon contact with the wall, an unbalanced force acts upon the car to abruptly decelerate it to rest. Any passengers in the car will also be decelerated to rest if they are strapped to the car by seat belts. Being strapped tightly to the car, the passengers share the same state of motion as the car. As the car accelerates, the passengers accelerate with it; as the car decelerates, the passengers decelerate with it; and as the car maintains a constant speed, the passengers maintain a constant speed as well.
But what would happen if the passengers were not wearing the seat belt? What motion would the passengers undergo if they failed to use their seat belts and the car were brought to a sudden and abrupt halt by a collision with a wall? Were this scenario to occur, the passengers would no longer share the same state of motion as the car. The use of the seat belt assures that the forces necessary for accelerated and decelerated motion exist. Yet, if the seat belt is not used, the passengers are more likely to maintain its state of motion.
Can you relate Newton's other 2 laws to this video? Explain.
Newton's Laws of Motion Rap
Newton's Laws Flickr Project
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Phenomena: Walking with Giants - The Moai Stone Heads
How did the Moai people move the huge stone heads on Easter Island?
Machines are not always metal, but any device that helps make work easier.
What Is Mechanical Advantage?
How much a machine changes the input force is its mechanical advantage. Mechanical advantage is the ratio of the output force to the input force, so it can be represented by the equation:
Actual Mechanical Advantage
=Output force/Input force
Note that this equation represents the actual mechanical advantage of a machine. The actual mechanical advantage takes into account the amount of the input force that is used to overcome friction. The equation yields the factor by which the machine changes the input force when the machine is actually used in the real world.
Ideal Mechanical Advantage
It can be difficult to measure the input and output forces needed to calculate the actual mechanical advantage of a machine. Generally, an unknown amount of the input force is used to overcome friction. It’s usually easier to measure the input and output distances than the input and output forces. The distance measurements can then be used to calculate the ideal mechanical advantage. The ideal mechanical advantage represents the change in input force that would be achieved by the machine if there were no friction to overcome. The ideal mechanical advantage is always greater than the actual mechanical advantage because all machines have to overcome friction. Ideal mechanical advantage can be calculated with the equation:
= Input Distance/Output Distance
A Simple Example
Look at the ramp in the Figure below. A ramp is a type of simple machine called an inclined plane. It can be used to raise an object off the ground. The input distance is the length of the sloped surface of the ramp. This is the distance over which the input force is applied. The output distance is the height of the ramp, or the vertical distance the object is raised. For this ramp, the input distance is 6 m and the output distance is 2 meters. Therefore, the ideal mechanical advantage of this ramp is:
Ideal Mechanical Advantage = Input distance = 6 m = 3
Output distance 2 m
An ideal mechanical advantage of 3 means that the ramp ideally (in the absence of friction) multiplies the input force by a factor of 3. The trade-off is that the input force must be applied over a greater distance than the object is lifted.
Machines are not always metal, but any device that helps make work easier.
What Is Mechanical Advantage?
How much a machine changes the input force is its mechanical advantage. Mechanical advantage is the ratio of the output force to the input force, so it can be represented by the equation:
Actual Mechanical Advantage
=Output force/Input force
Note that this equation represents the actual mechanical advantage of a machine. The actual mechanical advantage takes into account the amount of the input force that is used to overcome friction. The equation yields the factor by which the machine changes the input force when the machine is actually used in the real world.
Ideal Mechanical Advantage
It can be difficult to measure the input and output forces needed to calculate the actual mechanical advantage of a machine. Generally, an unknown amount of the input force is used to overcome friction. It’s usually easier to measure the input and output distances than the input and output forces. The distance measurements can then be used to calculate the ideal mechanical advantage. The ideal mechanical advantage represents the change in input force that would be achieved by the machine if there were no friction to overcome. The ideal mechanical advantage is always greater than the actual mechanical advantage because all machines have to overcome friction. Ideal mechanical advantage can be calculated with the equation:
= Input Distance/Output Distance
A Simple Example
Look at the ramp in the Figure below. A ramp is a type of simple machine called an inclined plane. It can be used to raise an object off the ground. The input distance is the length of the sloped surface of the ramp. This is the distance over which the input force is applied. The output distance is the height of the ramp, or the vertical distance the object is raised. For this ramp, the input distance is 6 m and the output distance is 2 meters. Therefore, the ideal mechanical advantage of this ramp is:
Ideal Mechanical Advantage = Input distance = 6 m = 3
Output distance 2 m
An ideal mechanical advantage of 3 means that the ramp ideally (in the absence of friction) multiplies the input force by a factor of 3. The trade-off is that the input force must be applied over a greater distance than the object is lifted.
Q: Assume that another ramp has a sloping surface of 8 m and a vertical height of 4 m. What is the ideal mechanical advantage of this ramp?
A: The ramp has an ideal mechanical advantage of:
Ideal Mechanical Advantage= 8 m = 2
4 m
Watch the video about mechanical advantage, and then solve the problems below.
A: The ramp has an ideal mechanical advantage of:
Ideal Mechanical Advantage= 8 m = 2
4 m
Watch the video about mechanical advantage, and then solve the problems below.