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