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Questions and Answers
What is a force?
What is a force?
A push or a pull on an object.
Which of the following is a unit for measuring force?
Which of the following is a unit for measuring force?
What direction does gravitational force point?
What direction does gravitational force point?
When is an object in equilibrium?
When is an object in equilibrium?
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What does Newton's First Law of Motion state?
What does Newton's First Law of Motion state?
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What does the negative sign in force indicate when using Newton's Second Law?
What does the negative sign in force indicate when using Newton's Second Law?
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What is the formula for calculating force?
What is the formula for calculating force?
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What occurs when one body exerts a force on a second body, according to Newton's Third Law?
What occurs when one body exerts a force on a second body, according to Newton's Third Law?
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What is a free body diagram?
What is a free body diagram?
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The unit for measuring mass is __________.
The unit for measuring mass is __________.
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How does air resistance affect the motion of objects?
How does air resistance affect the motion of objects?
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What is force?
What is force?
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Which of the following is a unit for force?
Which of the following is a unit for force?
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What are the three types of common forces described?
What are the three types of common forces described?
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What does the gravitational force act on?
What does the gravitational force act on?
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What is a Free Body Diagram?
What is a Free Body Diagram?
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The larger the area of the moving object, the less drag force it experiences.
The larger the area of the moving object, the less drag force it experiences.
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What is Newton's First Law of Motion?
What is Newton's First Law of Motion?
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What does it mean for an object to be in equilibrium?
What does it mean for an object to be in equilibrium?
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What is the equation for Newton's Second Law of Motion?
What is the equation for Newton's Second Law of Motion?
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What does the negative sign indicate in the context of force?
What does the negative sign indicate in the context of force?
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According to Newton’s Third Law, what happens for every action?
According to Newton’s Third Law, what happens for every action?
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Match the following terms with their definitions:
Match the following terms with their definitions:
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Study Notes
What is Force?
- Force is a push or pull on an object.
- A force has a magnitude (size) and a direction.
- Many types of forces can act on an object in different combinations.
- The symbol for force is F.
- The unit of measurement for force is the Newton (N).
Common Forces
- Gravitational Force (Fg): Acts on everything with mass. It’s the force between the Earth and another object, pointing towards the center of the Earth.
- Friction (Ff): Acts against motion or desired motion, depending on the surfaces involved.
- Normal Force (Fn): A perpendicular force that acts in response to a contact force, usually a surface pushing up on an object.
- Tension (Ft): Force from a rope, cable, etc., that can only pull (not push).
- Buoyancy (Fb): The upward force experienced by an object submerged in a fluid, equal to the weight of the fluid displaced.
- Water/Air Resistance (FDrag): Opposes the motion of an object in a fluid. It depends on fluid viscosity and the area of the object.
- Spring Force (FSp): The force exerted by a spring when compressed or stretched, opposing the change in length.
- Applied Force (FApplied): Any external force not specifically described.
Free Body Diagrams
- A free body diagram is a visual representation of forces acting on an object.
- Each force is drawn as an arrow originating from the object, with the arrow’s length representing the force’s strength.
Newton’s Three Laws of Motion
- Newton’s First Law of Motion (Law of Inertia): An object at rest will stay at rest, and an object in motion will stay in motion at a constant velocity unless acted upon by a net external force.
- Newton’s Second Law of Motion: The net force on an object is equal to its mass multiplied by its acceleration (F = ma).
- Newton’s Third Law of Motion (Law of Action-Reaction): For every action (force), there is an equal and opposite reaction.
Equilibrium
- An object is at equilibrium when all forces acting on it are balanced, resulting in no acceleration.
- The sum of all forces is zero.
Newton’s First Law of Motion Explained
- The first law explains inertia. An object at rest tends to stay at rest, and an object in motion tends to stay in motion at a constant velocity.
Forces and Motion (Examples)
- Example 1: A car moving at a constant speed with thrust force from the engine balanced by drag force (friction and air resistance).
- Example 2: A car hitting the brakes. The braking force creates an unbalanced force, causing the car to decelerate.
Newton's Second Law of Motion Explained
- Second law describes the relationship between force, mass, and acceleration.
- A heavier object requires more force to accelerate than a lighter object.
Newton’s Third Law of Motion Explained (Action and Reaction)
- If object A pushes on object B, object B pushes back on object A with an equal and opposite force.
- Examples: windshield/bug, student/Earth, bat/ball, rocket/gas
Action/Reaction Force Examples
- Windshield and bug: Windshield applies force to bug, bug applies force to windshield.
- Student and Earth: Student pushes down on Earth, Earth pushes up on student.
- Bat and ball: Bat hits ball, ball hits bat.
- Rocket and gases: Rocket pushes gases out the bottom, gases push up on the rocket.
What is Force?
- Force is a push or a pull on an object.
- It has both magnitude (size) and direction.
- There are many types of forces that can act on an object, both individually and in combination.
- The symbol for force is "F" and its unit is the Newton (N).
Common Forces
- Gravitational Force (FG): Acts on everything with mass, points towards the center of the Earth.
- Friction (FF): Resistive force that opposes motion or "desired" motion, depends on the surfaces involved.
- Normal Force (FN): Perpendicular force that acts in response to a contact force, typically a surface pushing up on an object.
- Tension (FT): Force from a rope, cable, etc., they can only pull, not push.
- Water/Air Resistance (FDrag): Opposes the motion of an object, depends on fluid viscosity (thickness) and the object's area.
- Bouyancy (FB): An upward force experienced by an object submerged in a fluid, equal to the weight of the fluid displaced.
- Spring Force (FSp): Force that opposes the compression or stretching of a spring.
- Applied Force (FApplied): Any external force not specifically described.
Free Body Diagram
- Illustrates forces acting on an object.
- Each force is drawn as an arrow originating from the object.
- Arrow length represents force strength.
Newton's Laws of Motion
- First Law: An object at rest stays at rest, and an object in motion stays in motion with constant velocity, unless acted upon by a net external force.
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Second Law: The acceleration of an object is directly proportional to the net force and inversely proportional to its mass.
- Equation: F = ma (where F = net force, m = mass, a = acceleration)
- Third Law: For every action (force) there is an equal and opposite reaction (force).
Equilibrium
- Occurs when all forces acting on an object are balanced, resulting in zero net force.
- An object in equilibrium has no acceleration and its velocity remains constant.
Newton's Second Law of Motion: Practice Problems
- Problem 1: A truck with a mass of 1500 kg accelerates at -5 m/s². The required force is -7500 N. The negative sign indicates the force is acting in the opposite direction of motion (braking).
- Problem 2: A ball with an acceleration of 2500 m/s² is hit with a force of 500 N. The ball's mass is 0.20 kg.
- Problem 3: A 10-kg cart is pulled with a force of 30 N. The cart's acceleration is 3 m/s².
- Problem 4: If the cart starts from rest and accelerates for 5 seconds, its final velocity is 15 m/s.
Newton's Third Law of Motion: Action & Reaction Forces
- When object A applies a force to object B (action), object B applies an equal and opposite force to object A (reaction).
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Examples:
- Windshield pushing on a bug, bug pushing on the windshield.
- Student pushing on Earth, Earth pushing on the student.
- Bat hitting a ball, ball hitting the bat.
- Rocket pushing out gas, gas pushing back on the rocket.
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Description
This quiz explores the concept of force, including its definition, types, and roles in physics. You will learn about various forces such as gravitational, frictional, and buoyant forces, along with their measurements and applications. Ideal for students studying introductory physics.
