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Chapter 11: Motion Motion- an object’s change in position relative to a reference point Frame of Reference- a system for specifying the precise location of objects in space and time.
Chapter 11: Motion Motion- an object’s change in position relative to a
reference point
Frame of Reference- a system for specifying the precise location of objects in space and time.
Chapter 11: Motion
Speed Animation
Chapter 11: Motion Distance- measures how far an objects moves along a
path.
Displacement- measures how far it is between ther starting an ending points.
Chapter 11: Motion speed- the distance traveled divided by the time
interval during which the motion occured
velocity- the speed of an object in a particular direction.
Chapter 11: Motion
Relative Motion Animation
Chapter 11: Motion
time
distancepeed s
t
dv
Chapter 11: Motion slope- The ratio of the vertical change to the
horizontal change between two points on a line. It measures the steepness of a line.
Chapter 11: Motion
run
riseslope
12
12
xx
yyslope
Chapter 11: Motion On a Distance vs. Time graph, the slope of the line
equals the speed of the car.
Chapter 11: Motion
Chapter 11: Motion
acceleration- the rate at which the velocity changes over time; an object accelerates if its speed, direction, or both change.
Chapter 11: Motion
Acceleration Animation
Chapter 11: MotionCentripetal Acceleration- the acceleration of an object that travels in a circle.
“Centripetal” mean center seeking
Chapter 11: Motion
Chapter 11: Motion
time
velocityinitial - velocity finalonaccelerati
t
vva
if
Chapter 11: Motion On a Speed vs. Time graph, the slope of the line equals
the acceleration of the object.
Chapter 11: Motion
Ball rolling down incline movie
Chapter 11: Motion
force- an action exerted on a body in order to change the body’s state of rest or motion; force has magnitude and direction.
Chapter 11: Motion
Four fundamental forces:
- Force of gravity
- Electromagnetic force
- Strong nuclear force
- Weak nuclear force
Chapter 11: Motion
Forces can act through contact or at a distance.
Contact Force
Any push or pull
Field Force (forces at a distance)
Gravity
Magnetism
Electric
Unbalanced Forces Cause… ?
A change in motion!
Meaning??
Acceleration!!
Balanced Forces cause… ?
Nothing!!!
If forces on an object are balanced, the object will keep
doing what it is doing.
To Review…What causes objects to accelerate?
Unbalanced Forces
What do unbalanced forces lead to?
Acceleration
More Review…What causes objects to keep doing
what they are doing?
Balanced Forces
What do balanced forces lead to?
Objects will stay at rest or at constant speed.
And Finally… What happens if the net force on an object is zero?
The object will keep doing what it is doing!
It will stay at rest OR it will keep moving at constant speed.
What happens if the net force on an object is not zero?
The object will change its motion!
This is acceleration!
What three things can happen for acceleration to occur?
Speed up, Slow down or change direction!!
Chapter 11: Motion
friction- a force that opposes motion between two surfaces that are in contact.
Chapter 11: Motion
Chapter 11: Motion
Chapter 11: Motion
Two types of Friction:
Kinetic Friction
Static Friction
Chapter 11: Motion
Kinetic friction is the frictional force between two surfaces that aremoving along each other.
Kinetic friction acts on objects that are sliding on a surface.
Chapter 11: Motion
Rolling Friction is a special type of kinetic friction.
Rolling Friction is the friction when a round objects rolls over a flat surface.
Chapter 11: Motion
Static friction is the frictional force between two surfaces that are notmoving along each other.
Static friction keeps objects on inclines from sliding, and keeps objects from moving when a force is first applied.
5.4 Friction
Chapter 11: Motion
Unwanted Friction can be lowered.
How?
Chapter 11: Motion
Helpful Friction can be lowered.
How?
