Download Force and Motion Force: a push or a pull that causes a change in

Force and Motion
Force: a push or a pull that causes a change in movement or shape
Example: Pushing a baby stroller
Pulling on a rope
Motion: the change in position of an object as compared to a fixed point
- Distance: length of the actual path traveled by an object
- Speed: distance traveled by an object in a given amount of time
- Velocity: object’s speed in a given direction
 Velocity (v) = distance (d) / time (t)
Example:
Speed = 80 miles per hour
Velocity = 80 miles per hour NORTH
Acceleration: a change in velocity over time.
- Acceleration of an object in a free fall on the Earth:
 = 9.8 m/s2
3 Forces that affect Motion
1) Friction: A force that resists the motion of 2 surfaces/objects touching each
other; slows down or prevents motion.
Example: car tires on a road surface
2) Gravity: Force of attraction between 2 or more objects;
Weight is a measure of the force of gravity on an object.
 Rate of acceleration (free fall) is constant because of gravity’s pull.
3) Upward Force: a force used to support something.
Example: If a book is resting on a table, the table is exerting an upward
force on the book.
Example with all three Forces:
r = upward force of ramp
g = gravity’s pull down
f = friction between car and ramp
Other Forces
Net Force: the sum of all the forces acting on an object.
Balanced Forces: when the total of all forces equal zero; no change in motion.
Net Force = ZERO
Unbalanced Forces: when the total of all forces DOES NOT equal zero; produce a
change in motion
Net Force = greater than zero
 Forces must be unbalanced to change an object’s motion.
Newton’s First Law of Motion:
-
An object at rest remains at rest until an unbalanced force acts on it.
-
An object moving at a constant speed and in a straight line will continue to
do so until an unbalanced force acts on it.
-
1st Law is also known as Inertia.
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Inertia depends on an objects mass- the greater the mass, the greater the
force needed to cause a change in motion.
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Inertia (definition)- tendency of an object to remain at rest or in motion.
(DEPENDS ON ITS MASS)
-
The force needed to stop a moving object depends on both its mass and
velocity.
Momentum
-
The tendency of an object to keep moving in the same direction at the same
speed; object’s mass multiplied by its velocity.
-
MASS x VELOCITY
**The Law of Conservation of Momentum**
-
Momentum can be transferred between objects but the total momentum is
NEVER LOST.
Newton’s Second Law of Motion:
-
An unbalanced force on an object causes the object to accelerate in the
direction of the force. **Newtons (N)
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The greater the force applied to an object, the greater its acceleration.
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The greater the mass of an object, the greater its acceleration.
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Mass- affects how much force is needed to accelerate an object. (Think
about the video with kicking the bowling ball and soccer ball.
-
The greater the mass, the more force is needed to move an object.
-
Mass (definition)- The amount of matter in an object.
**FORMULA- F= MA
F= Applied Force (measured in kg/g)
M= Mass (measured in m/s)
A= Acceleration (measured in m/s or m/s^2 or km/hr)
Examples of 2nd Law:
1. Use the gas pedal to make a car go faster
2. An Ice Skater pushes harder with her leg muscles and she begins to move
faster.
-
All falling objects on Earth accelerate at 9.8 meters/second squared!
-
Acceleration- Change in an object’s speed or direction over time (a change in
velocity)
**FORMULA- A= Vf-Vi
T
A= Acceleration
Vf= Final Velocity
Vi- Initial Velocity (starting)
T-Time
Newton’s 3rd Law of Motion:
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For every action by force there is an equal and opposite reaction by another
force.
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Forces act in pairs: Action/Reaction
-
Forces act on different objects.
Examples:
UP (ROCKET) Moving in opposite direction= Reaction Force
Down (HOT GASES) escaping= Action Force
Road pushes on wheels= Reaction Force
Wheels push on Road=Action
Centripetal Acceleration-
Definition- The acceleration of an object moving in curved path or circle at a
constant speed.
Example: Satellite orbiting the Earth Loop of a Rollercoaster.
Centripetal Force
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Definition- Force that is directed toward the center of a circle which keeps
an object moving in a circle instead of flying away.
-
This is the force that causes Centripetal Acceleration.
Example: Gravity between the Moon and Earth provides centripetal
force that pulls the moon towards the center of Earth, keeping it in
orbit.