NLM - Introduction to Newton's Laws of Motion
Newton's Laws of Motion
Introduction
From kinematics we progress to dynamics. Up until now we have only dealt with a description of motion. We will now turn to the causes of motion. Newton's first law will be used to discuss inertia. Newton's second law will allow us to create equations to relate the force or forces acting on an object and the change in motion that occurs. Newton's third law will allow us to determine what object's forces are applied to. We will then study some of the basic forces that are often applied to objects. These will include weight, friction, and the normal force. By the end of this unit, students should be able to calculate the acceleration for objects that touch or are tied to each other and for objects that are on inclines under the influence of friction, gravity, and other external forces.
Essential Questions
- What is the relationship between forces when an object is at rest or moving with a constant velocity?
- What is the velocity change when an object moving in one dimension has a constant force F act on it for a specified time interval.
- What is the velocity change when an object moving in one dimension has a force F(t) act on it for a specified time interval?
- What is the average force that acts on an object moving in a plane whose vector undergoes a specified change over time?
- What is the free body diagram for the forces acting on an object?
- What is the vector equation that results from applying Newton's Second Law to an object, and what are the components of this equation?
- When an object moves with a specified acceleration under the influence of one or more forces, what is the net force, or one of the forces?
- What is the relationship between the normal and frictional forces on a surface?
- What is the motion of an object moving under the influence of friction?
- What is the magnitude of the force of static friction?
- What is the terminal velocity of an object moving vertically under the influence of a drag force?
- What is the motion of a particle moving under the influence of a drag force?
- What is the differential equation for the velocity of a particle under the influence of a drag force?
- What is the equation for the velocity as a function of time from the differential equation for an object experiencing a drag force?
- What is an equation for the acceleration as a function of time for an object falling under the influence of drag forces?
- For a given system, what are action/reaction forces, the magnitude and direction of the forces, and the objects on which they act?
- What is the force of contact between two objects that accelerate together along a horizontal or vertical line, or between two surfaces that slide across each other?
- What is the tension on a light string that passes over a massless pulley and what is the motion of a system of two objects joined by this string?
- How can problems in which Newton's laws lead to two or three simultaneous linear equations be used to solve for unknown forces or accelerations?
Key Terms
- Force - Anything that pushes or pulls on an object.
- Free Body Diagram - A diagram that shows forces on an object in the form of arrows in the direction of the force.
- Friction - A force between two surfaces that resists the sliding of the two surfaces past each other.
- Normal - The force of a surface pushing on the object perpendicular to the surface.
- Weight - The force of gravity pulling on the mass of an object.
- Coefficient of Friction - The ratio of frictional force to the normal force on an object.
- Mass - A measurement of the amount of matter in a substance.
- Inertia - The amount an object resists a change in motion. Measured by the mass of the object.
- Center of Mass - The unique point where the weighted relative position of the distributed mass sums to zero. This is the point to which a force may be applied to cause a linear acceleration without an angular acceleration.
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