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Questions and Answers
What is a reference point?
What is a reference point?
A reference point is a place or object used for comparison to determine whether something is in motion.
What are three reference points you can use to determine if someone on a roller coaster is moving?
What are three reference points you can use to determine if someone on a roller coaster is moving?
Motion is relative.
Motion is relative.
True (A)
What are the two ways a force can be described?
What are the two ways a force can be described?
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What is the unit for the strength of a force in the International System of Units (SI)?
What is the unit for the strength of a force in the International System of Units (SI)?
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What does the length of an arrow in a force diagram represent?
What does the length of an arrow in a force diagram represent?
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What is a contact force?
What is a contact force?
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What is the contact force that occurs when two surfaces rub against each other?
What is the contact force that occurs when two surfaces rub against each other?
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What is gravity?
What is gravity?
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What is a balanced force?
What is a balanced force?
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What is the net force on an object?
What is the net force on an object?
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If a force is acting on an object, the object must be moving.
If a force is acting on an object, the object must be moving.
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The weaker the force, the shorter the arrow representing it in a force diagram.
The weaker the force, the shorter the arrow representing it in a force diagram.
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Which of these scenarios best describes a contact force?
Which of these scenarios best describes a contact force?
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Friction can be a contact force.
Friction can be a contact force.
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Friction is a force that always opposes motion.
Friction is a force that always opposes motion.
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Gravity is a contact force.
Gravity is a contact force.
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Which of the following is NOT a noncontact force?
Which of the following is NOT a noncontact force?
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If there is an unbalanced force acting on an object, the object will change its speed, direction, or both.
If there is an unbalanced force acting on an object, the object will change its speed, direction, or both.
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If the net force on an object is zero, then the forces on the object must be balanced.
If the net force on an object is zero, then the forces on the object must be balanced.
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Balanced forces are the only forces acting on a stationary object.
Balanced forces are the only forces acting on a stationary object.
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A book sliding across a table at a constant speed is acted upon by balanced forces.
A book sliding across a table at a constant speed is acted upon by balanced forces.
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If an object accelerates in the direction of the larger force, what can we conclude about the forces acting on the object?
If an object accelerates in the direction of the larger force, what can we conclude about the forces acting on the object?
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Describe how the forces acting on a tug-of-war rope can be balanced. Describe how those forces can be unbalanced.
Describe how the forces acting on a tug-of-war rope can be balanced. Describe how those forces can be unbalanced.
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In the diagram with the two chipmunks pushing on an apple with a net force of 0 N, which of the following is the most likely reason the apple does not move?
In the diagram with the two chipmunks pushing on an apple with a net force of 0 N, which of the following is the most likely reason the apple does not move?
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In the diagram with the chipmunk and squirrel pushing on the apple with a net force of 4N, what determines the direction in which the apple is likely to move?
In the diagram with the chipmunk and squirrel pushing on the apple with a net force of 4N, what determines the direction in which the apple is likely to move?
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When a net force is acting on an object, the object must be moving.
When a net force is acting on an object, the object must be moving.
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Describe the forces acting on a girl picking up a bag of apples from the ground.
Describe the forces acting on a girl picking up a bag of apples from the ground.
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Balanced forces would cause an object to move in a straight line at a constant speed.
Balanced forces would cause an object to move in a straight line at a constant speed.
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If the net force is zero, then the object will stay at rest, or if it is in motion, continue moving at the same speed and in the same direction.
If the net force is zero, then the object will stay at rest, or if it is in motion, continue moving at the same speed and in the same direction.
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Flashcards
Motion
Motion
An object is in motion if its position changes compared to another object.
Reference Point
Reference Point
A place or object used to determine if something is in motion.
Relative Motion
Relative Motion
Motion that depends on the chosen reference point.
Force
Force
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Strength of Force
Strength of Force
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Direction of Force
Direction of Force
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Newton (N)
Newton (N)
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Contact Forces
Contact Forces
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Friction
Friction
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Noncontact Forces
Noncontact Forces
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Gravity
Gravity
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Balanced Forces
Balanced Forces
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Unbalanced Forces
Unbalanced Forces
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Net Force
Net Force
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Static Friction
Static Friction
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Kinetic Friction
Kinetic Friction
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Force Diagram
Force Diagram
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Motion Change
Motion Change
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Direction of Motion
Direction of Motion
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Inertia
Inertia
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Acceleration
Acceleration
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Deceleration
Deceleration
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Speed
Speed
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Velocity
Velocity
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Momentum
Momentum
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Equal Forces
Equal Forces
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Resultant Force
Resultant Force
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Force Applied
Force Applied
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Study Notes
School Information
- School name: Britus Education Castle International School
- Identifiable by logo of a shield with a dark blue design.
Science Book Course 3 - Lesson 1
- Topic: Describing Motion and Force
- Page numbers: 120-126 in Science Book (SB)
Table of Contents
- An Object in Motion
- Reference Point
- Relative Motion
- How Forces Affect Motion
- Describing Force
- Types of Forces
- Balanced and Unbalanced Forces
An Object in Motion - Reference Point
- An object is in motion when its position changes relative to another object.
- A reference point is a place or object used to determine if something is moving.
- Examples of good reference points are objects fixed to Earth, such as trees, buildings, or stop signs.
Reading Check - Determine Conclusions
- Example: If you are in a car with a dog, the car itself or another person in the car can be a reference point to determine if the dog is moving.
Relative Motion
- Motion is relative because it depends on the chosen reference point.
- A reference point can change.
- Example: On a beach, using a beach towel as a reference point, you aren't moving because your position does not change relative to the towel. However, if you choose the sun as the reference point, you are moving because Earth moves around the sun.
Reading Check - Draw Evidence
- Sources of information to determine Earth's relative motion compared to other planets in the solar system include online information about the speeds and locations of all the planets.
Relative Motion (Figure 2)
- In motion relative to : the track, a person standing on the ground, the sun
- Stationary relative to : another person on the ride, the seat, the car
How Forces Affect Motion
- Objects in motion can change speed, slow down, or change direction when forces act upon them.
- A force is a push or a pull.
- When one object pushes or pulls another, the first object exerts a force on the second object.
Describing Force
- Forces are described by their strength and direction.
- Force is measured in Newtons (N) in the International System of Units.
- Stronger forces have longer arrows in diagrams, while weaker forces have shorter arrows to represent the direction.
Describing Force (Figure 3)
- Arrows (vectors) indicate the force's direction.
- Example: In the diagram, a bird sitting on an elephant shows a small downward force by the bird.
Infer - Which Image Shows a Force ...
- Image 2 (a horse pulling a cart) shows a force that causes a change in motion.
- The horse is strong enough to pull the cart, causing it to move, whereas the forces on the elephant and the dog in the other images are not strong enough to move them.
Types of Forces
- Forces are categorized as contact or non-contact forces.
- Contact forces only work when objects touch each other. Example: pushing a box.
- Friction is a contact force that occurs when two surfaces rub against each other. It opposes motion on a surface.
Types of Forces
- Non-contact forces work without touching the object Example: Gravity
- Gravity is a non-contact force pulling objects towards each other due to their mass.
- Other examples of non-contact forces are magnetism and electrical forces.
Reading Check - Identify Noncontact Forces
- Examples of non-contact forces are gravity, magnetism, and electrical forces.
Types of Forces (Figure 4)
- The girl in the bicycle image is exerting a force on the pedals, a contact force.
- Friction is a contact force between the tires of the bicycle and the road.
- Gravity, pulling the girl downward, is a non-contact force.
Balanced and Unbalanced Forces
- Balanced forces have equal strength and act in opposite directions, resulting in a zero net force.
- Unbalanced forces have unequal strength or act in the same direction. This causes a change in motion.
Balanced and Unbalanced Forces
- The net force on an object is the combination of all forces acting on it.
- If forces are in the same direction, add them; if in opposite direction, subtract.
- If net force is zero, forces are balanced.
Model It! - Forces in Tug-of-War
- The stronger team is determined by greater frictional forces acting on them from the ground.
Math Toolbox - Effects of Net Force
- Forces cause changes in motion.
- Balanced forces result in zero net force.
- Unbalanced forces cause changes in motion.
- The net force equals the difference or sum depending on the directions.
Reading Check - Infer (Apple Bag)
- The force of lifting the bag of apples is stronger than the force of gravity, acting in the opposite direction.
Homework
- Lesson Check, page 127 in the Science Book (SB).
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Description
Explore the concepts of motion and force with this quiz based on Science Book Course 3. Learn about reference points, relative motion, and the types of forces that affect how objects move. Test your understanding of balanced and unbalanced forces as well.
