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Is an _____ exerted on an object in order to change the object’s ________ or ______ A push or pull in other words It has magnitude & direction What does that mean? Force can be balanced or unbalanced
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Motion & Force
Objectives Describe how forces act upon objects
and create motion Describe how friction influences the
motion Explain the different types of friction Explain why friction is important
Force Is an _____ exerted on an object in
order to change the object’s ________ or ______
A push or pull in other words It has magnitude & direction What does that mean?
Force can be balanced or unbalanced
Balanced & U
nbalanced Forces
Balanced ForcesU
nbalanced Forces
Balanced forces occur when the forces applied to an object produce a net force of zero
They do not cause a change in the motion of an object or move an object out of rest
Example: a hat on your head
Unbalanced forces occur when forces do not cancel out completely
They cause a change in the motion of an object
Because the net force is greater than zero the object will accelerate in the direction of the greater force
The Force of Friction Friction is the force that opposes
motion between 2 surfaces that are in contact
Friction happens because the surface of any object is rough (microscopically speaking)
Friction opposes the applied force on an object
Friction also affects objects that aren’t moving
Friction Causes Acceleration
When a car is accelerating, the forces are __________________› The force moving the car forward is greater
than the opposing force of friction When a car is cruising at a constant
speed, the force moving the car forward is ___________ by the force of friction
Balanced forces could also mean that the car is not in motion
2 Types of FrictionKinetic Friction
Is the force of friction against an object already in ______
There are different kinds of kinetic friction› Sliding friction› Rolling friction› Fluid friction
Static Friction Is the force of
friction opposing the initial movement of an object from ________________
It is _______ than kinetic force
Types of Kinetic Friction ___________ is the friction that occurs between
objects that are sliding past each other ____________ is the friction of a round object
rolling over a flat surface› It is usually less than sliding friction
___________ is the friction of a moving object traveling through a fluid (a liquid or a gas)› It can be minimized by very smooth
surfaces› When air is the fluid, the force of
friction is called ___________
The Importance of Friction Why is friction important?
How can friction cause problems?
Reducing Harmful Friction1. Using lubricants such as motor oil, wax and grease› Lubricants are usually liquids but
can be solids or gases2. Replacing sliding friction with rolling
friction› Such as using ball bearings between
wheels and axles3. Make surfaces smoother
Increasing Helpful Friction
1. Making surfaces rougher2. Increase the force pushing the
surfaces together