# Physics Force Notes

Topics: Friction, Force, Mass Pages: 9 (2382 words) Published: October 10, 2013
﻿1. A book is at rest on a tabletop. A free-body diagram for this situation looks like this:

2. A girl is suspended motionless from the ceiling by two ropes. A free-body diagram for this situation looks like this:

3. An egg is free-falling from a nest in a tree. Neglect air resistance. A free-body diagram for this situation looks like this:

4. A flying squirrel is gliding (no wing flaps) from a tree to the ground at constant velocity. Consider air resistance. A free-body diagram for this situation looks like this:

5. A rightward force is applied to a book in order to move it across a desk with a rightward acceleration. Consider frictional forces. Neglect air resistance. A free-body diagram for this situation looks like this:

6. A rightward force is applied to a book in order to move it across a desk at constant velocity. Consider frictional forces. Neglect air resistance. A free-body diagram for this situation looks like this:

7. A college student rests a backpack upon his shoulder. The pack is suspended motionless by one strap from one shoulder. A free-body diagram for this situation looks like this:

8. A skydiver is descending with a constant velocity. Consider air resistance. A free-body diagram for this situation looks like this:

9. A force is applied to the right to drag a sled across loosely packed snow with a rightward acceleration. A free-body diagram for this situation looks like this:

10. A football is moving upwards towards its peak after having been booted by the punter. A free-body diagram for this situation looks like this:

11. A car is coasting to the right and slowing down. A free-body diagram for this situation looks like this:

(and Symbol)
Description of Force
Applied Force
Fapp
An applied force is a force that is applied to an object by a person or another object. If a person is pushing a desk across the room, then there is an applied force acting upon the object. The applied force is the force exerted on the desk by the person. Return to Top

Gravity Force
(also known as Weight)
Fgrav
The force of gravity is the force with which the earth, moon, or other massively large object attracts another object towards itself. By definition, this is the weight of the object. All objects upon earth experience a force of gravity that is directed "downward" towards the center of the earth. The force of gravity on earth is always equal to the weight of the object as found by the equation: Fgrav = m * g

where g = 9.8 N/kg (on Earth)
and m = mass (in kg)
(Caution: do not confuse weight with mass.)
Normal Force
Fnorm
The normal force is the support force exerted upon an object that is in contact with another stable object. For example, if a book is resting upon a surface, then the surface is exerting an upward force upon the...

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