# data[].attributes.body
The amount of friction depends on the force pushing two surfaces together.

# data[].attributes.body
Friction can cause a moving object to slow down and eventually stop.

# data[].attributes.body
Rough surfaces have more microscopic hills and valleys than smooth surfaces do

# data[].attributes.headline
Example of a surface with little friction is

# data[].attributes.subject
Example of a surface with little friction is

# data[].attributes.body
A ball rolling on the ground

# data[].attributes.body
Make surfaces rougher such as putting sand on icy roads to keep cars from slipping everywhere

# data[].attributes.body
Let's your writing show up on paper
you don't slip when you walk

# data[].attributes.body
Holes in socks
Wear down car parts
holes in jeans
cause erosion

# data[].attributes.body
Motor oil, wax, grease

# data[].attributes.body
Lubricants reduce friction they are substances applied to surfaces to reduce the friction between the surfaces.

# data[].attributes.body
Kilogram (kg)

# data[].attributes.body
The moons gravitational force is one-sixth of Earth's

# data[].attributes.body
Weight changes when gravitational force changes

# data[].attributes.body
Gravitational force decreases as distance increases

# data[].attributes.body
Force increases as mass increases

# data[].attributes.body
All objects in the universe attract each other through gravitational force

# data[].attributes.body
We are not affected by gravity. The gravity is pulling us down.

# data[].attributes.body
Mass is affected by gravity.Gravitational force pulls objects toward each other.

# data[].attributes.body
A measure of the amount of matter in an object.

# data[].attributes.body
A measure of the gravitational force exerted on an object; it's value can change with the location of the object in the universe.

# data[].attributes.body
The size of the force depends on the masses of the objects and the distance between objects.

# data[].attributes.body
A force of attraction between objects that is due to their masses.

# data[].attributes.body
Friction while sliding something means moving

# data[].attributes.body
When a force is applied to an object but does not cause the object to move means not moving

# data[].attributes.body
A force that opposes motion between two surfaces that are in contact.

# data[].attributes.body
The forces are unbalanced and produces a change in motion, so it moves.

# data[].attributes.body
The forces are balanced and do not change in motion.

# data[].attributes.body
Gravity

# data[].attributes.body
Newtons

# data[].attributes.body
The si unit for force (Symbol N),

# data[].attributes.body
The combination of all of the forces acting on an object

# data[].attributes.body
A push or pull exerted on an object in order to change the motion of the object, force has size and dierection

# data[].attributes.attachment_link.readable_text
Free-body diagrams are diagrams used to show the relative magnitude and direction of all forces acting upon an object in a given situation. A free-body diagram is a special example of the vector diagrams that were discussed in an earlier unit. These diagrams will be used throughout our study of physics. The size of the arrow in a free-body diagram reflects the magnitude of the force. The direction of the arrow shows the direction that the force is acting. Each force arrow in the diagram is labeled to indicate the exact type of force. It is generally customary in a free-body diagram to represent the object by a box and to draw the force arrow from the center of the box outward in the direction that the force is acting. An example of a free-body diagram is shown at the right

T he free-body diagram above depicts four forces acting upon the object. Objects do not necessarily always have four forces acting upon them. There will be cases in which the number of forces depicted by a free-body diagram will be one, two, or three. There is no hard and fast rule about the number of forces that must be drawn in a free-body diagram. The only rule for drawing free-body diagrams is to depict all the forces that exist for that object in the given situation. Thus, to construct free-body diagrams, it is extremely important to know the various types of forces. If given a description of a physical situation, begin by using your understanding of the force types to identify which forces are present. Then determine the direction in which each force is acting. Finally, draw a box and add arrows for each existing force in the appropriate direction; label each force arrow according to its type. If necessary, refer to the list of forces and their description in order to understand the various force types and their appropriate symbols.

We Would Like to Suggest ...

Sometimes it isn't enough to just read about it. You have to interact with it! And that's exactly what you do when you use one of The Physics Classroom's Interactives. We would like to suggest that you combine the reading of this page with the use of our Free-Body Diagram Interactive. You can find it in the Physics Interactives section of our website. The Free-Body Diagram Interactive allows a learner to practice identifying the forces that act upon an object and to express such an understanding by the construction of a free-body diagram.

Practice

Apply the method described in the paragraph above to construct free-body diagrams for the various situations described below. Answers are shown and explained at the bottom of this page.

1. A book is at rest on a tabletop. Diagram the forces acting on the book. See answer.

2. A gymnast holding onto a bar, is suspended motionless in mid-air. The bar is supported by two ropes that attach to the ceiling. Diagram the forces acting on the combination of gymnast and bar. See answer.

3. An egg is free-falling from a nest in a tree. Neglect air resistance. Diagram the forces acting on the egg as it is falling. See answer.

4. A flying squirrel is gliding (no wing flaps) from a tree to the ground at constant velocity. Consider air resistance. Diagram the forces acting on the squirrel. See answer.

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. Diagram the forces acting on the book. See answer.

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. Diagram the forces acting on the book. See answer.

7. A college student rests a backpack upon his shoulder. The pack is suspended motionless by one strap from one shoulder. Diagram the vertical forces acting on the backpack. See answer.

8. A skydiver is descending with a constant velocity. Consider air resistance. Diagram the forces acting upon the skydiver. See answer.

9. A force is applied to the right to drag a sled across loosely packed snow with a rightward acceleration. Neglect air resistance. Diagram the forces acting upon the sled. See answer.

10. A football is moving upwards towards its peak after having been booted by the punter. Neglect air resistance. Diagram the forces acting upon the football as it rises upward towards its peak. See answer.

11. A car is coasting to the right and slowing down. Neglect air resistance. Diagram the forces acting upon the car. See answer.

Answers

Answers to the above exercise are shown here. If you have difficulty drawing free-body diagrams, then you ought to be concerned. Continue to review the the list of forces and their description and this page in order to gain a comfort with constructing free-body diagrams.

1. A book is at rest on a tabletop. A free-body diagram for this situation looks like this:

2. A gymnast holding onto a bar, is suspended motionless in mid-air. The bar is supported by two ropes that attach to the ceiling. Diagram the forces acting on the combination of gymnast and bar. 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. Neglect air resistance. 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. Neglect air resistance. A free-body diagram for this situation looks like this:

Return to Questions Return to Info on Free-body diagrams Return to on-line Force Description List

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

Return to Questions Return to Info on Free-body diagrams
Return to on-line Force Description List

# data[].attributes.attachment_link.description
The motion of objects is determined by the relative size and the direction of the forces that act upon it. Free-body diagrams showing these forces, their direction, and their relative magnitude are often used to depict such information. In this Lesson, The Physics Classroom discusses the details of constructing free-body diagrams. Several examples are discussed.

# data[].attributes.body
Final velocity minus starting velocity divided by time it takes to change velocity

# data[].attributes.body
Factors important to velocity is speed and direction

# data[].attributes.body
total distance divided by total time

# data[].attributes.body
Meters per second

# data[].attributes.body
object that appears to stay in place.

# data[].attributes.body
The rate at which velocity changes overtime an object accelerates if it's speed, direction, or both change

# data[].attributes.body
The speed of an object in a particular direction

# data[].attributes.body
The distance traveled divided by the time interval during which the motion occurred.

# data[].attributes.body
An objects change in position relative to a reference point

# data[].attributes.body
A force that opposes motion