Newton’s Laws of Motion

Sir Isaac Newton Born January 4, 1643 in England As a young student, Newton didn’t do well in school. He worked hard and continued his education. Later in life, Newton contributed ideas that became law in the worlds of science and math.

Newton’s Law of Inertia “An object at rest, tends to stay at rest, and an object in motion, tends to stay in motion with the same speed and in the same direction, unless acted upon by an outside force.” Objects resist change in motion. The more mass an object has, the greater its inertia.

Newton’s Law of Force and Acceleration F = ma Net force on object = mass of object x acceleration Which vehicle will accelerate more quickly? Why? It takes more force to move an object with a larger mass, and it accelerates at a slower pace. However, once moving, it is more difficult to stop. It takes less force to move an object with a smaller mass, and it accelerates at a faster pace. It will come to a stop easier than a more massive object. With the same force, as the mass of an object increases, the acceleration decreases.

For Example… If the force remains constant, smaller masses will have greater acceleration compared to larger masses. If the force remains constant, larger masses will have less acceleration compared to smaller masses. F=ma F=ma

For Example… Small Mass = Greater Acceleration Large Mass = Less Acceleration Force is same for different masses. Larger masses are slower to accelerate, and smaller masses are quicker to accelerate.

Newton’s Law of Force and Acceleration If the mass of an object remains constant, then acceleration increases as the force increases. ALWAYS identify the force, mass, and acceleration variables to see which ones are constant. Mass is the constant with different amounts of force. If the mass of two objects is equal and the forces applied to them are different, then the object with the larger force will have greater acceleration.

Force Force (N) = mass (kg) x acceleration (m/s2) F = ma The equation F=ma is the base equation for any force, mass, and acceleration problems.

Write the initial equation: F = ma Decide what you are solving for: So, what happens if you are trying to see how fast a force can accelerate a particular mass?? Write the initial equation: F = ma Decide what you are solving for: acceleration Use math to restructure the equation: m m Instructional Note: By the 3rd six weeks, students should have the mathematical skills to manipulate formulas. This concept will be new to the students because they have not applied this algebraic concept to a situation yet. This is a great way to reinforce the skill for mathematics and prepare students for physics. Show students how to manipulate a formula. Start by deciding what is being solved for: in this case, it is acceleration and a will need to be by itself in the equation. In F=ma the mass is being multiplied by the acceleration. The opposite operation of multiplication is division. Therefore, mass will need to be divided on both sides of the equation. The triangle used in the last lesson may be utilized for students who need more scaffolding.

The equation for acceleration is: a = F m So, what happens if you are trying to see how fast a force can accelerate a particular mass?? The equation for acceleration is: a = F m But does the equation make sense?? What happens to the acceleration of a bicycle if the force is increased (pedal harder)?? What happens to the acceleration of a bicycle if the mass is increased (having to pull friends on rollerblades)?? After mass has been divided on both sides of the equation, it would read a=F/m. After students have manipulated the equation to solve for a, have students check to see if the equation makes sense. The faster you pedal, the faster the bike will accelerate. The more people you are dragging, the slower the bike will accelerate.

This can be done to find the mass of an object being accelerated with a particular force. Write the initial equation: F = ma Decide what you are solving for: mass Use math to restructure the equation: a a Show students how to manipulate a formula. Start by deciding what is being solved for: in this case, it is mass and m will need to be by itself in the equation. In F=ma, the mass is being multiplied by the acceleration. The opposite operation of multiplication is division. Therefore, acceleration will need to be divided on both sides of the equation.

The equation for mass is: m = F a Does it make sense? So, what happens if you are trying to see how fast a force can accelerate a particular mass?? The equation for mass is: m = F a Does it make sense? After acceleration has been divided on both sides of the equation, it would read m=F/a. After students have manipulated the equation to solve for m, have students check to see if the equation makes sense. Have students create their own examples for this scenerio.

Newton’s Law of Action-Reaction "For every action, there is an equal and opposite reaction." Reaction Action

Newton’s Law of Action-Reaction All forces act in pairs. When one object exerts a force on a second object, the second object exerts an equal and opposite force on the first object. This is not a cause-effect relationship. The forces occur simultaneously.