Physics Lab
Physics Lab
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Newton's 2nd Law

*Newton's 1st and 2nd laws are now split up into two pages.

Newton's 1st law of motion told us why objects accelerate (or don't accelerate) due to a net force. But how do we calculate the actual value of the acceleration? And how exactly is it related to the net force? That's where we need Newton's 2nd law of motion.

Newton's 2nd Law of Motion: ΣF = ma, the net force acting on an object is equal to its mass multiplied by its acceleration. The acceleration is in the same direction as the net force.

The famous equation that we get from Newton's 2nd Law, ΣF = ma, is the foundation for this unit and a lot of physics. It also takes care of Newton's 1st law of motion conceptually: if there's no net force then there's no acceleration, so an object at rest will remain at rest and an object in motion will have a constant velocity.

We're going to start with a conceptual understanding of Newton's 2nd law and introduce a new concept: mass. An object's mass is a measure of its inertia, so objects with more mass have more inertia and are more resistant to a change in their state of motion. Think about pushing an empty grocery cart and a full grocery cart - which one is harder to move and turn around corners?

Then we'll learn how to draw a free body diagram and apply Newton's 2nd law equation in 1D and 2D. Just like we learned in kinematics, the x and y directions are independent, so we can write ΣF = ma for the x direction and the y direction to get two equations. Then we can use those equations to solve for any value we want to find.

Newton's 2nd Law of Motion (19:09)
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Intro to Newton's 2nd law of motion

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Net force, mass and acceleration

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Calculate the acceleration and net force

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3 key points about Newton's 2nd law of motion

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Proportional reasoning: how changing one variable affects the others

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How Newton's 2nd law replaces Newton's 1st law
Newton's 2nd Law and Free Body Diagrams in 2D (25:27)
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Newton's 2nd law in 2 dimensions

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How to find the x and y acceleration components

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Combining the net force and acceleration components

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Why do objects move in the x or y direction?

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Example 1: multiple forces in each direction

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Example 2: working with forces at an angle

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Steps for drawing a FBD and applying Newton's 2nd law

Study guide for how to draw free body diagrams and label force vectors
Study guide for Newton's 2nd law of motion and how to use a free body diagram to determine the acceleration of a mass
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Newton's 2nd Law of Motion
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Multiple-Choice Questions

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Newton's 1st law of motion told us why objects accelerate (or don't accelerate) due to a net force. But how do we calculate the actual value of the acceleration? And how exactly is it related to the net force? That's where we need Newton's 2nd law of motion.

Newton's 2nd Law of Motion: ΣF = ma, the net force acting on an object is equal to its mass multiplied by its acceleration. The acceleration is in the same direction as the net force.

The famous equation that we get from Newton's 2nd Law, ΣF = ma, is the foundation for this unit and a lot of physics. It also takes care of Newton's 1st law of motion conceptually: if there's no net force then there's no acceleration, so an object at rest will remain at rest and an object in motion will have a constant velocity.

We're going to start with a conceptual understanding of Newton's 2nd law and introduce a new concept: mass. An object's mass is a measure of its inertia, so objects with more mass have more inertia and are more resistant to a change in their state of motion. Think about pushing an empty grocery cart and a full grocery cart - which one is harder to move and turn around corners?

Then we'll learn how to draw a free body diagram and apply Newton's 2nd law equation in 1D and 2D. Just like we learned in kinematics, the x and y directions are independent, so we can write ΣF = ma for the x direction and the y direction to get two equations. Then we can use those equations to solve for any value we want to find.

Newton's 2nd Law of Motion
Preview of the AP Physics 1 multiple choice questions (MCQ) for Newton's 1st and 2nd laws of motion
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