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Questions and Answers
A car is moving at a constant velocity. According to Newton's First Law, what is required to change the car's velocity?
A car is moving at a constant velocity. According to Newton's First Law, what is required to change the car's velocity?
- A decrease in the car's mass.
- No force is required to maintain constant velocity.
- An external force acting on the car. (correct)
- A constant force in the direction of motion.
Two objects, one with a mass of 2kg and the other with a mass of 4kg, are subjected to the same force. According to Newton's Second Law, how will their accelerations compare?
Two objects, one with a mass of 2kg and the other with a mass of 4kg, are subjected to the same force. According to Newton's Second Law, how will their accelerations compare?
- The accelerations will be inversely proportional to the square of their masses.
- Both objects will have the same acceleration.
- The 2kg object will have twice the acceleration of the 4kg object. (correct)
- The 4kg object will have twice the acceleration of the 2kg object.
A book rests on a table. Which of the following statements best describes the reaction force, as defined by Newton's Third Law?
A book rests on a table. Which of the following statements best describes the reaction force, as defined by Newton's Third Law?
- The force exerted by the book on the table. (correct)
- The force exerted by the Earth on the table.
- The force of gravity pulling the book downwards.
- The combined weight of the book and the table.
Which of the following scenarios best illustrates the concept of inertia?
Which of the following scenarios best illustrates the concept of inertia?
A rocket in space expels exhaust gases. How does this demonstrate Newton's Third Law?
A rocket in space expels exhaust gases. How does this demonstrate Newton's Third Law?
A box is being pushed across a rough floor at a constant speed. What can be concluded about the forces acting on the box?
A box is being pushed across a rough floor at a constant speed. What can be concluded about the forces acting on the box?
An astronaut is using a wrench to tighten a bolt on the International Space Station. Considering Newton's Third Law, what happens as the astronaut turns the wrench?
An astronaut is using a wrench to tighten a bolt on the International Space Station. Considering Newton's Third Law, what happens as the astronaut turns the wrench?
In what type of scenarios do Newton's Laws of Motion begin to lose accuracy and require modification or replacement with other theories?
In what type of scenarios do Newton's Laws of Motion begin to lose accuracy and require modification or replacement with other theories?
A projectile is launched into the air. Assuming air resistance is negligible, what is the primary force acting on the projectile during its flight?
A projectile is launched into the air. Assuming air resistance is negligible, what is the primary force acting on the projectile during its flight?
A satellite is orbiting the Earth in a circular path. Which of the following forces is primarily responsible for maintaining this circular motion?
A satellite is orbiting the Earth in a circular path. Which of the following forces is primarily responsible for maintaining this circular motion?
Flashcards
Newton's First Law
Newton's First Law
An object remains at rest, or in motion at a constant velocity, unless acted upon by a net external force.
Newton's Second Law
Newton's Second Law
The acceleration of an object is directly proportional to the net force acting on it, and inversely proportional to its mass.
Newton's Third Law
Newton's Third Law
For every action, there is an equal and opposite reaction.
Inertia
Inertia
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Inertial Frame of Reference
Inertial Frame of Reference
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Projectile Motion
Projectile Motion
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Circular Motion
Circular Motion
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Rocket Propulsion
Rocket Propulsion
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Limitations of Newton's Laws
Limitations of Newton's Laws
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Study Notes
- Newton's laws of motion describe the relationship between a body, the forces acting on it, and its motion in response to those forces.
- These laws form the foundation for classical mechanics.
Newton's First Law - Law of Inertia
- An object at rest stays at rest, and an object in motion stays in motion with the same speed and in the same direction unless acted upon by a force.
- This law defines inertia as the tendency of an object to resist changes in its state of motion.
- Inertia is directly proportional to an object's mass; the more massive, the more inertia.
- Newton's first law is only valid in inertial frames of reference.
- An inertial frame is one that is not accelerating or rotating.
- It's where an object not subject to forces will move at a constant velocity.
Newton's Second Law - Law of Acceleration
- The acceleration of an object is directly proportional to the net force acting on it and in the same direction as the net force, and inversely proportional to the object's mass.
- This is expressed as F = ma, where F is the net force, m is the mass, and a is the acceleration.
- Force is a vector quantity with both magnitude and direction.
- The net force is the vector sum of all forces acting on the object.
- Acceleration direction is the same as the net force direction.
- The SI unit of force is the Newton (N), defined as 1 kg⋅m/s².
Newton's Third Law - Law of Action-Reaction
- For every action, there is an equal and opposite reaction.
- When one object exerts a force on another, the second object exerts an equal force in the opposite direction on the first object.
- Forces always occur in pairs; a single isolated force cannot exist.
- Action and reaction forces act on different objects.
- They are equal in magnitude and opposite in direction.
- These forces do not cancel each other out.
- When walking, a person pushes backward on the Earth (action), and the Earth pushes forward on the person (reaction).
Applications of Newton's Laws
- Projectile Motion involves analyzing the motion of objects launched into the air, with gravity as the main force.
- Circular Motion explains the motion of objects moving in a circle and introduces centripetal force and acceleration.
- Rocket Propulsion describes how rockets generate thrust by expelling exhaust gases, using Newton's third law.
Limitations of Newton's Laws
- Newtonian mechanics is an approximation suitable for everyday situations.
- It breaks down at very high speeds (near the speed of light) due to relativistic effects.
- General Relativity is needed when gravity is extremely strong, such as near black holes.
- It also fails at very small scales (atomic and subatomic) requiring quantum mechanics.
- Newtonian mechanics assumes constant mass, but mass can change with velocity, as per special relativity.
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