Forces and Motion

Motion  What do you think it means to be in motion?  How can we tell if something is in motion?  How can we provide evidence?

Motion  Motion: a change in position, measured by distance and time.  Motion: a change in position, measured by distance and time.

Frame of Reference Determining if an object changes position requires a frame of reference. Determining if an object changes position requires a frame of reference. The object or point from which movement is determined The object or point from which movement is determined  ks/ml_science_share/vis_sim/ mfm05_pg7_relmotion/mfm05_ pg7_relmotion.html ks/ml_science_share/vis_sim/ mfm05_pg7_relmotion/mfm05_ pg7_relmotion.html ks/ml_science_share/vis_sim/ mfm05_pg7_relmotion/mfm05_ pg7_relmotion.html What is the frame of reference for this video? How do I know the skater is in motion?

Frame of Reference  Movement is relative to an object that appears stationary  Earth is the most common frame of reference

Speed  Speed: the distance traveled by a moving object per unit of time To calculate speed, use the equation Speed = distance / time  Speed only gives distance and time!

Average Speed  Average speed: the speed of moving objects is not always constant  To calculate average speed you look at total time and distance Average speed = total distance / total time

Velocity  Velocity is speed in a given direction.  Velocity gives distance, time, and the direction of travel.  Velocity changes by changing direction or changing speed! st minute

Velocity is speed with direction

Why do I care?  Understanding an object’s motion can help you understand how to interact with the world around you.

Review  What is the frame of reference for the sunset?  What is a frame of reference?  What is the most common frame of reference?

Calvin and Hobbes

Calculate Calvin and Hobbes’ Speed.

 S= D/T  50 yd/ 10 min  5 yd/min

Average Speed  1. What is your average speed if you take 2h to jog 8 miles ?  Speed= distance/ time  8m/2h= 4 mph  2. What is the average speed of a car if it travels 500 miles in 20 hours?  Speed= distance/ time 500miles/20h = 25 mph 500miles/20h = 25 mph

Force Force: any push or pull

Forces are measured in _____ Forces are measured in _____ A _____ is the combination of all of the forces acting on an object. A _____ is the combination of all of the forces acting on an object.

Forces

Force  Balanced Forces forces acting on an object that are opposite in direction and equal in size no change in velocity

Balanced vs. Unbalanced Forces Balanced forces will not cause a change in the motion of an object; they have a net force of zero N.  Examples of balanced forces are:  1. ______, 2. _____, 3. _____.

Balanced vs. Unbalanced forces  Unbalanced forces could be best described as __________________________.  Examples of unbalanced forces are ___________________________.

Force Drawing  Create a drawing that shows an example of balanced forces. The drawing should show the forces acting on the object and what happens to the object if the forces become unbalanced.

Forces

Forces  You and a younger brother or sister are at a neighborhood pool. Your brother or sister asks why there are signs that say “NO RUNNING!” What would be your answer?

Forces  _____, ______, and ______ are examples of common lubricants.  Therefore, it is easier to slip when there is water on the floor because the water acts as a ______ that lessens the friction between the bottom of your shoe and the floor.

NSF North Mississippi GK-8 Pushing pedals, pressing brakes, and kicking soccer balls are all examples of forces. A force is anything that changes the velocity of an object. But what’s a change in velocity ? A change in velocity is acceleration, so... A force is anything that gives an object acceleration.

Friction  _____ is a force that opposes motion between two surfaces that are in contact.  A _____ is a substance that lessens friction.

Friction  Friction force that opposes motion between 2 surfaces force that opposes motion between 2 surfaces depends on the: depends on the: types of surfacestypes of surfaces force between the surfacesforce between the surfaces A _____ is a substance A _____ is a substance that lessens friction.

Friction  There are four types of friction.

Friction  Four Types of Friction Static Friction – force that acts on objects that are not moving. (Couch Potato) Static Friction – force that acts on objects that are not moving. (Couch Potato) Sliding Friction - force that opposes the direction of motion of an object as it slides over a surface. (Ice skating or bobsledding) Sliding Friction - force that opposes the direction of motion of an object as it slides over a surface. (Ice skating or bobsledding) Rolling Friction – friction force that acts on rolling objects. (Rollerblading) Rolling Friction – friction force that acts on rolling objects. (Rollerblading) Fluid Friction – force that opposes the motion of an object through a fluid. (Planes flying or submarines traveling) Fluid Friction – force that opposes the motion of an object through a fluid. (Planes flying or submarines traveling)

Friction  Write a story that describes what a day in your life would be like if there was no friction.

 Gravity

Gravity  Isaac Newton discovered the ______ ______ of Gravitation.  Gravity acts on any objects with mass. Example: You and your books, pencils, paper, etc.

Universal Law of Gravitation  Mass and gravity have a directly proportional relationship.  The distance between the centers of masses of the two objects and gravity have an inversely proportional relationship.

Differentiate between Mass and Weight.  Weight is dependent upon the acceleration due to gravity on a particular planet.  For instance: g on earth is 9.8 m/s²  The larger the planet, the _____ the gravitational force.