Chapter 5: Newton's Laws of Motion Reference Tools & Resources

Reference Tools & Resources

I. Key Terms and Phrases

dynamics: the branch of physics that studies force and the causes of various types of motion.

force: a push or a pull applied to an object.

mass: a measure of an object's inertia.

inertia: an object's natural tendency to move with constant velocity.

inertial reference frame: a frame of reference in which the law of inertia holds.

free-body diagram: a diagram of an isolated object showing all the force vectors acting on the object.

weight: the downward force due to gravity.

apparent weight: the perceived weight of an object as its force of contact with the ground or a scale.

normal force: the component of the contact force on a surface that is perpendicular to the surface.

II. Important Equations

Name/Topic	Equation	Explanation
Newton's second law		The vector sum of all forces acting on an object equals its mass times its acceleration.
inclined surfaces		The components of an object's weight on a surface inclined at an angle to the horizontal.

III. Know Your Units

Quantity	Dimension	SI Unit
force		N

IV. Other Useful Tips

You may have noticed that in the free-body diagrams in the above examples the forces are always drawn with their tails on the idealized body and their heads pointing away. This is the usual tradition and it is better to be consistent. So always draw the forces on your free-body diagrams with tails on the body and heads pointing away from the body.

Reference Tools and Resources by David Reid, Eastern Michigan University. ©2002 by Prentice Hall, Inc.

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