1. PEPS Rainier Jr/Sr High School Mr. Taylor
Chapter 11: Motion
PEPS
Rainier Jr/Sr High School
Mr. Taylor

2. Measuring Motion (Ch 11.1)
Motion is always measured against a frame of reference; an object or point used for comparison.
When an object changes position with respect to a frame of reference, the object is in motion.
Distance is how far the object moves along a path.

3. Speed vs Velocity Speed describes how fast an object moves.
Velocity tells both speed AND direction the object moves.
Speed = distance ÷ time
Speed is measured in meters/second (SI units), but could be miles/hour, inches/year, etc.

4. Graphing Motion Motion is studied using distance/time graphs.
Time is the independent variable; distance is the dependent variable.
A steeper slope indicates faster speeds.
A slope of zero indicates the object is not in motion.

5. Acceleration (Ch 11.2) Acceleration is a change in velocity.
A change in speed is acceleration.
A change in direction is acceleration.
Acceleration = (final velocity – initial velocity) ÷ time
A = (vf –vi) ÷ t
SI units are meters/second/second or m/sec/sec or m/sec2 (These are all the same thing…)

6. Centripetal acceleration
Centripetal acceleration is the force generated by a constant change of direction (in other words; circular motion).

7. Graphing Acceleration
The slope of the line of a speed/time graph is the acceleration.
A steeper slope is faster acceleration.
A positive slope is speeding up; a negative slope is slowing down.
Acceleration seen on a distance/time graph is a curved line when the acceleration ≠ 0 (zero).

8. Motion and Force (Ch 11.3)
A force is any action that changes the motion of an object.
There are 4 fundamental forces in Nature:
Gravity
Electromagnetic forces
Strong nuclear force
Weak nuclear force

9. Balanced and Unbalanced Forces
Net force is the sum of all forces acting on an object.
Balanced forces have a net force of zero and do not cause any change in an object’s motion.
Unbalanced forces have a net force > zero and cause the object to change motion in the direction of the unbalanced force.

10. Friction
Friction is a force that always acts in the opposite direction of motion.
Static friction exists between surfaces in contact with each other and are not moving.
Kinetic friction exists between surfaces in contact with each other that are moving.
Sliding friction: the two surfaces are sliding past each other.
Rolling friction: one surface is rolling over the other.
Fluid friction: one surface is solid and the other is fluid (a liquid or a gas).

11. May
the Force
be with you!