Force and Motion

Day 1

What is a force

Forces are a push or a pull on an object. If the forces are balanced the object will not move. If the forces are unbalanced the object will move.

Carson has been riding a scooter for almost as long as he can remember. He can even do tricks in the air. It takes a lot of practice to be able to control a scooter like this. Carson automatically applies just the right forces to control his scooter.

Defining Force

Force is defined as a push or pull acting on an object. There are several fundamental forces in the universe, including the force of gravity, electromagnetic force, and weak and strong nuclear forces. When it comes to the motion of everyday objects, however, the forces of interest include mainly gravity, friction, and applied force. Applied force is force that a person or thing applies to an object.

Q : What forces act on Carson’s scooter?

A : Gravity, friction, and applied forces all act on Carson’s scooter. Gravity keeps pulling both Carson and the scooter toward the ground. Friction between the wheels of the scooter and the ground prevent the scooter from sliding but also slow it down. In addition, Carson applies forces to his scooter to control its speed and direction.

What is friction?https://www.youtube.com/watch?v=MAqrWvkBoHk

This explains what a Newton is. http://www.gamequarium.org/cgi-bin/search/linfo.cgi?id=6935

What is weight?

Weight is just another word for the force of gravity. . Weight is a force that acts at all times on all objects near Earth. The Earth pulls on all objects with a force of gravity downward toward the center of the Earth.The weight of an object will change if the object is brought farther away from Earth, or placed on a different planet, since the force of gravity on the object will be smaller. However the mass of the object will remain the same regardless of whether the object is on Earth, in outer space, or on the Moon.

What is your weight on other planets?http://www.exploratorium.edu/ronh/weight/

Force and Motion

Forces cause all motions. Every time the motion of an object changes, it’s because a force has been applied to it. Force can cause a stationary object to start moving or a moving object to change its speed or direction or both. A change in the speed or direction of an object is called acceleration. Look at Carson’s brother Colton in the Figure below . He’s getting his scooter started by pushing off with his foot. The force he applies to the ground with his foot starts the scooter moving in the opposite direction. The harder he pushes against the ground, the faster the scooter will go.

How much an object accelerates when a force is applied to it depends not only on the strength of the force but also on the object’s mass. For example, a heavier scooter would be harder to accelerate. Colton would have to push with more force to start it moving and move it faster. You can explore the how force, mass, and acceleration are related by doing the activity at this URL:

Activity 1 Copy the chart then go to the site for the online lab

Force 1 N Force 2 N Force 3N Force 4 N

1

2

3

4

Site http://www.harcourtschool.com/activity/newton/

Q : What units do you think are used to measure force?

A : The SI unit for force is the Newton (N). A Newton is the force needed to cause a mass of 1 kilogram to accelerate at 1 m/s ² , so a Newton equals 1 kg • m/s ² . The Newton was named for the scientist Sir Isaac Newton, who is famous for his laws of motion and gravity.

Activity 2 Write vocabulary cards for the following words: force, motion, friction, inertia, gravity, air resistance, Newton

Day 2

Force as a Vector

Force is a vector, or a measure that has both size and direction. For example, Colton pushes on the ground in the opposite direction that the scooter moves, so that’s the direction of the force he is applies. He can give the scooter a strong push or a weak push. That’s the size of the force. Like other vectors, a force can be represented with an arrow. You can see some examples in the Figure below . The length of each arrow represents the strength of the force, and the way the arrow points represents the direction of the force.

Q : How could you use arrows to represent the forces that start Colton’s scooter moving?

A : Colton pushes against the ground behind him The ground pushes back with equal force to the left, causing the scooter to move in that direction.

Summary

• Force is defined as a push or pull acting on an object. Forces include gravity, friction, and applied force.

• Force causes changes in the speed or direction of motion. These changes are called acceleration.

• The SI unit for force is the Newton (N).

• Force is a vector because it has both size and direction. Like other vectors, it can be represented by an arrow.

Explore More

Activity 1:

1. Draw a diagram to represent a foot kicking a resting soccer ball. Use arrows to represent the force applied to the ball and to show how the ball moves after it is kicked. To see an animation of this force and motion, go to the URL below.

http://www.3m.co.uk/intl/uk/3mstreetwise/pupils-force.htm

Apply different types of forces to materials in the interactive animated lab at the following URL. Then answer the questions below.

http://www.pbs.org/wgbh/buildingbig/lab/forces.html

1. What is compression, and how does it affect materials?

2. What is tension? What is a real-life example?

3. Describe shear as a force.

4. What is torsion?

Review

1. What is force?

2. Relate force and motion.

3. What forces control the motion of everyday objects?

4. Identify and define the SI unit for force.

What is force? http://www.gamequarium.org/cgi-bin/search/linfo.cgi?id=3762

http://www.abc.net.au/science/video/2013/08/06/3811724.htm

Moon Olympics game about gravity http://teacher.scholastic.com/activities/explorations/space/level1/MoonOlympics.htm

Brain Pop:Force and Motion

https://www.brainpop.com/science/motionsforcesandtime/force/preview.weml

Full episode about friction. https://www.youtube.com/watch?v=utVwbki_Li8

Extra: Forces=

Go to the following website: Read the passage and take the quiz at the end. When you are done, play the game. http://www.bbc.co.uk/bitesize/ks2/science/physical_processes/forces/read/1/

Sound:

Go to the following website: Read the passage and take the quiz at the end. When you are done, play the game.

http://www.bbc.co.uk/bitesize/ks2/science/physical_processes/sound/read/1/

Parkworld Module

http://www-g.eng.cam.ac.uk/mmg/teaching/peterstidwill/interact/resources/parkworldplot.htm

Link to Parkworld viewing questions is at the bottom.

Vocabulary:

acceleration= change in speed or direction- m/s/s, velocity= a speed and direction,

speed= a distant and time relationship mph, m/s

displacement= a distance and a direction 6m N.

work= A result of a force moving an object a certain distance., Joules

power= work divided by the time it takes, watts

force= a push or a pull on an object, N

Motion= An object's change in position relative to a reference point.

momentum= the force or speed with which something moves

mass x velocity

Extra Files:

Forces notes and practice problems.docx (24k)Kathy Dougherty, Feb 5, 2017, 3:58 PM

Newtons Laws practice sheet.doc (27k)Kathy Dougherty, Mar 6, 2015, 3:21 PM

Parkworld question guide.doc (24k)Kathy Dougherty, Feb 15, 2015, 1:04 PM

Motion

The wings of this hummingbird are moving so fast that they’re just a blur of motion. You can probably think of many other examples of things in motion. If you can’t, just look around you. It’s likely that you’ll see something moving, and if nothing else, your eyes will be moving. So you know from experience what motion is. No doubt it seems like a fairly simple concept. However, when you read this article, you’ll find out that it’s not quite as simple as it seems.

Defining Motion

In science, motion is defined as a change in position. An object’s position is its location. Besides the wings of the hummingbird in opening image, you can see other examples of motion in the Figure below . In each case, the position of something is changing.

Q : In each picture in the Figure above , what is moving and how is its position changing?

A : The train and all its passengers are speeding straight down a track to the next station. The man and his bike are racing along a curving highway. The geese are flying over their wetland environment. The meteor is shooting through the atmosphere toward Earth, burning up as it goes.

Frame of Reference

There’s more to motion than objects simply changing position. You’ll see why when you consider the following example. Assume that the school bus pictured in the Figure below passes by you as you stand on the sidewalk. It’s obvious to you that the bus is moving, but what about to the children inside the bus? The bus isn’t moving relative to them, and if they look at the other children sitting on the bus, they won’t appear to be moving either. If the ride is really smooth, the children may only be able to tell that the bus is moving by looking out the window and seeing you and the trees whizzing by.

This example shows that how we perceive motion depends on our frame of reference. Frame of reference refers to something that is not moving with respect to an observer that can be used to detect motion. For the children on the bus, if they use other children riding the bus as their frame of reference, they do not appear to be moving. But if they use objects outside the bus as their frame of reference, they can tell they are moving. The video at the URL below illustrates other examples of how frame of reference is related to motion.

http://www.youtube.com/watch?v=7FYBG5GSklU

Q : What is your frame of reference if you are standing on the sidewalk and see the bus go by? How can you tell that the bus is moving?

A : Your frame of reference might be the trees and other stationary objects across the street. As the bus goes by, it momentarily blocks your view of these objects, and this helps you detect the bus’ motion.

Summary

Motion is defined as a change of position.

How we perceive motion depends on our frame of reference. Frame of reference refers to something that is not moving with respect to an observer that can be used to detect motion.

Explore More

What is motion? video

http://www.gamequarium.org/cgi-bin/search/linfo.cgi?id=6938

Review

1. How is motion defined in science?

2. Describe an original example that shows how frame of reference influences the perception of motion

3. Activity 1 Lab http://www.harcourtschool.com/activity/newton/index.html

4. Copy the following chart in your notebook. Calculate the difference traveled between each second and write it in the third column. Create a graph showing the information. Explain what is happening in each section of the graph. Support it with evidence from your chart.

5. 
   

time distance difference?

1 5

2 10

3 15

4 20

5 20

6 20

7 25

8 32

9 41

10 15

Activity 2 notes on acceleration http://www.physicsclassroom.com/class/1DKin/Lesson-3/The-Meaning-of-Shape-for-a-p-t-Graph

Activity 3 Practicing graphing http://www.physicsclassroom.com/mmedia/kinema/acceln.cfm

constant positive velocity
http://www.physicsclassroom.com/mmedia/kinema/cpv.cfm
Activity: graph that motion
http://www.physicsclassroom.com/Physics-Interactives/1-D-Kinematics/Graph-That-Motion

Extra Files:

Velocity3.2Worksheet.pdf (1117k)Kathy Dougherty, Feb 15, 2016, 8:31 PM

speed and time worksheet.pdf (839k)