Questions and Answers
What will happen to an object in motion unless acted upon by an unbalanced force?
An object at rest stays at rest.
True
What do free-body diagrams show?
Relative magnitude and direction of all forces acting on an object.
What can be said about gravity when an egg is free-falling from a nest?
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What forces act on a flying squirrel gliding to the ground?
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An unbalanced force exists when the vertical and horizontal forces do not ______.
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What does the second law of motion state?
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What happens to a football moving upwards toward its peak?
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What effects act on a car coasting down a hill?
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What does the third law of motion state?
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Study Notes
Newton's Laws of Motion
- An object in motion continues in motion in a straight line unless acted upon by an unbalanced force.
- An object at rest will remain at rest until acted upon by an external force.
- Unbalanced forces result when vertical and horizontal forces do not cancel each other out.
Free Body Diagrams (FBD)
- Free body diagrams illustrate the magnitude and direction of all forces acting on an object.
- Useful for visualizing how different forces interact in various scenarios.
Force Interaction Examples
- Book on a Table: The forces acting on a stationary book include gravitational force downward and normal force upward.
- Flying Squirrel: Gravity pulls down while air resistance acts upward during a glide at constant velocity.
- Falling Egg: In free fall, gravity is the sole force acting on the egg (air resistance ignored).
- Moving Book: An applied rightward force moves the book; friction acts leftward. Gravity and normal forces are also present.
- Skydiver: Gravity pulls down while air resistance counteracts the force during descent with constant velocity.
- Man Dragging Sled: Rightward applied force is countered by friction leftward; gravity and normal forces also apply.
- Upward Moving Football: Only the force of gravity acts as it rises (no air resistance considered).
- Coasting Car: Gravity and normal forces act on a car, with additional friction opposing motion downhill.
Newton's Laws Recap
- 1st Law: An object remains at rest or in uniform motion unless acted upon by a net external force.
- 2nd Law: Acceleration of an object is directly proportional to the net force acting on it and inversely proportional to its mass (F = ma).
- 3rd Law: For every action, there is an equal and opposite reaction, meaning forces occur in pairs.
Important Concepts
- Air resistance can significantly affect the motion of falling or gliding objects.
- Friction is a critical force countering motion in various scenarios, affecting the applied forces.
- Understanding these principles is essential for analyzing motion and forces in physical systems.
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Test your understanding of free-body diagrams with these flashcards. Each card highlights key concepts related to forces and motion, including how objects behave under various conditions. Perfect for students learning physics concepts in dynamics.
