Drawing Free Body Diagrams Worksheet Answers Physics Classroom

Day #: Newton's 3rd law of motion

By the end of this unit students should be able to state Newton's 3rd law of motion and identify "action-reaction" force pairs.

Demo: Air pucks

As stated by Newton

:
"To every action there is always

opposed an equal reaction

: Or the mutual attractions of two bodies upon each other are always equal, and directed to contrary parts."

Force pairs: Which force is stronger?

Website (Physics Classroom): Newton's 3rd law

Website (Hyperphysics): Newton's laws

Video (Science 360): Science of Football collisions

Tutorial (Khan Academy): Newton's 3rd law

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Topic #: Basic Free-Body diagrams

By the end of this unit students should be able draw free-body diagrams for various basic (horizontal & vertical surfaces) situations .

Demo: topic

A free body diagram, sometimes called a force diagram, is a pictorial device, often a rough working sketch, used by engineers and physicists to analyze the forces and moments acting on a body. The body itself may consist of multiple components, an automobile for example, or just a part of a component, a short section of a beam for example, anything in fact that may be considered to act as a single body, if only briefly. A whole series of such diagrams may be necessary to analyze forces in a complex problem. A free body diagram, or FBD, is not meant to be a scaled drawing. Rather it is a working sketch open to modification as one works through the problem and typically one needs to have seen through the problem before one arrives at a satisfactory diagram.

Website (Hyperphysics): Free-body diagrams

Website (Physics Classroom): Free-body diagrams

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Tutorial (Bozeman Science): Free-body diagrams

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Day #: Free-body diagrams of an object on an incline

By the end of this unit students should be able to draw complex free body diagrams of objects on an incline.

Demo: Inclined plane and block

Whenever you have an object sitting on a surface you always have two forces acting on it. The force of gravity (F_g or W) and the normal force (F_N or N). When the surface is an incline, those two forces still exist. Gravity still is directly downward and the normal is still directed upward, perpendicular to the surface.

When the angle of incline increases, the gravitational force can thought of as breaking into components. The horizontal (or X) component is directed parallel to the surface and down the ramp. The vertical (or Y) component is perpendicular to the surface and opposite of the normal. In fact, the magnitude of the normal is equal to the vertical component of gravity (F_g cos θ)

The frictional force is directed up and parallel to the incline directly opposite to the horizontal component of gravity (F_g cos θ).

Website (Hyperphysics): topic

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Tutorial (Khan Academy): Inclined plane force components

Handout/Practice skills: Free-body diagrams (key)

Activity: Chapter 4 book problems - 40, 41, 44, 51, 60

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Day #: Topic

By the end of this unit students should be able to

Text

Picture

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