2016 Junior Lesson One

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Elfrieda McGee
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2016 Junior Lesson One To complete this lesson make sure you answer all the questions in bold and do one of the projects at the end of the lesson. Parts marked ADVANCED are for the curious.

Three important concepts which we will study are FORCE, WORK, and SIMPLE MACHINES. What are WORK and FORCE? FORCE is the push or pull one object has on another object.

Like many words in science the word WORK means something a little different than our everyday understanding of work.

1 2016 Junior Lesson One To complete this lesson make sure you answer all the questions in bold and do one of the projects at the end of the lesson. Parts marked ADVANCED are for the curious. This year we will study PHYSICS. PHYSICS is the science which studies matter and how matter moves through space and time. Three important concepts which we will study are FORCE, WORK, and SIMPLE MACHINES. What are WORK and FORCE? FORCE is the push or pull one object has on another object. For example, if you pull a wagon or push a buggy you are applying FORCE to the wagon or buggy. Like many words in science the word WORK means something a little different than our everyday understanding of work. WORK is done when a FORCE causes an object to move or change direction (called DISPLACEMENT). Here are some examples of WORK: Horse pulling a plow Force horse pulling Object plow Movement plow moves forward Cartoon character lifting barbells Force character lifting Object barbells Movement - barbells move upwards Athlete throwing a javelin Force athlete throwing Object javelin Movement -javelin moves forward Rocket moving through space Force expelled gases pushing rocket Object rocket Movement - rocket moves forward In the cartoon to the left, who has done the most WORK? The person (blue) pushing on the 300 kilogram ball but not moving it? or the person (red) making the 100 kilogram ball move forward 6 meters? Be careful how you answer. Consider, did the 300 kg ball move? Who did the most WORK, red or blue? Explain why: From Remember, no matter how hard the blue person s ball is pushed, if it does not move, there is NO WORK done.

Lesson One - Page 2 In SCIENCE it is important to be able to measure things, like WORK. If we know how far the object moved and the FORCE, we can measure the WORK.

html In order to lift the barbell above his head, the weight lifter needs to apply a FORCE which opposes the downward acting FORCE of gravity on the MASS of the barbell.

MASS of barbell = 25 kilograms+ 25 kilograms= 50 kilograms Weight of barbell = MASS x acceleration due to gravity Weight = MASS x gravity Weight = 50 kilograms x 9.

People understood the idea of weight a long time ago and gravity is almost the same everywhere on Earth. We don t notice any difference between the weight and MASS of something.

All objects have MASS. The MASS of an object never changes, no matter where in the universe you are. However, the WEIGHT of the object depends very much on where you are.

HOWEVER, the WEIGHT of the barbells depends on how hard gravity is pulling on the barbells. This depends on where you are. On Earth, the MASS of the barbells is multiplied by 9.

2 Lesson One - Page 2 In SCIENCE it is important to be able to measure things, like WORK. If we know how far the object moved and the FORCE, we can measure the WORK. The equation used is: WORK done = FORCE x distance The units of measurement are: Joule Newton meter Below adapted from In order to lift the barbell above his head, the weight lifter needs to apply a FORCE which opposes the downward acting FORCE of gravity on the MASS of the barbell. The distance from the floor to above the lifter s head is 2 meters. MASS of barbell = 25 kilograms+ 25 kilograms= 50 kilograms Weight of barbell = MASS x acceleration due to gravity Weight = MASS x gravity Weight = 50 kilograms x 9.8 = 490 Newtons WORK done = FORCE x distance WORK done = 490 Newtons x 2 meters = 980 Joules In our everyday lives we use the word WEIGHT instead of MASS. Why? People understood the idea of weight a long time ago and gravity is almost the same everywhere on Earth. We don t notice any difference between the weight and MASS of something. ADVANCED In the equation above we have to calculate FORCE and do this using the MASS and WEIGHT of the barbells. These words are words we again use differently in science and our everyday lives. All objects have MASS. The MASS of an object never changes, no matter where in the universe you are. However, the WEIGHT of the object depends very much on where you are. The MASS of the barbell is 50 kilograms (about 110 pounds). The barbells would have this MASS if we were on the moon or even in space. HOWEVER, the WEIGHT of the barbells depends on how hard gravity is pulling on the barbells. This depends on where you are. On Earth, the MASS of the barbells is multiplied by 9.8 Newton to calculate its WEIGHT. Gravity makes a 1 kilogram MASS exert 9.8 Newtons of FORCE. Knowing the FORCE allows us to calculate the WORK done by the athlete when he lifts the barbells in the example above. Let s look at how much the barbells would WEIGH elsewhere in our universe. Where On Earth On the Moon In deep space On Jupiter Mass 50 kg* 50 kg* 50 kg* 50 kg* Weight 490 Newtons or 110 lbs. 80 Newtons 18 lbs. 0 Newton or 0 lb Newtons or lbs. *Please remember, although we use kilograms and grams in our everyday lives to measure weight, these are really measures of MASS. To learn more go to

Lesson One- Page 3 Gravity Friend or Enemy? How much do you think astronauts carried while working on the moon? Neil Armstrong weighed 360 lbs.

But, there are problems for astronauts working at lower gravities. (Hint, what happens to the muscles of astronauts while in space?

If it is not too big, we can push it out of the way. If it is too big, we may not be able to move the rock - unless we have help. Help can be in the form of a tool.

But with the lever he can move the rock. The lever acts as an extension of his body. The lever makes it possible for the man to move the rock he is not strong enough to move on his own.

A hammer is a SIMPLE MACHINE, another example of a lever. The handle increases the force applied to the nail. Also, the head of the hammer is larger than the head of the nail.

3 Lesson One- Page 3 Gravity Friend or Enemy? How much do you think astronauts carried while working on the moon? Neil Armstrong weighed 360 lbs. in his moon suit and equipment while on Earth, but on the moon he only weighed 60 lbs. This made it easier to move around and do the important tasks he had to do. But, there are problems for astronauts working at lower gravities. (Hint, what happens to the muscles of astronauts while in space?) Do you know what they are: There are lots of types of WORK we have to do. For example, if we have a large rock in a field, we may need to move the rock. If it is not too big, we can push it out of the way. If it is too big, we may not be able to move the rock - unless we have help. Help can be in the form of a tool. In the drawing to the left you can see a man moving a large rock using a lever, a type of SIMPLE MACHINE. Without the lever he may not be able to move the rock, or do WORK. But with the lever he can move the rock. The lever acts as an extension of his body. The lever makes it possible for the man to move the rock he is not strong enough to move on his own. Another MACHINE is shown below. But, what if you had a hammer, could you push the nail into the wall? Would you be able to push a nail into the wall with just your hand? A hammer is a SIMPLE MACHINE, another example of a lever. The handle increases the force applied to the nail. Also, the head of the hammer is larger than the head of the nail. All the force from the head of the hammer will now go to the small head of the nail a lot of force and enough to push it into the wall. In PHYSICS tools like a lever are called SIMPLE MACHINES. Again, we have a word which means something a little different in science than in our everyday language. What do you think of when you hear the word MACHINE? In science a MACHINE is anything that is used to apply a FORCE. SIMPLE MACHINES change the direction or amount of FORCE. SIMPLE MACHINES make WORK easier.

Lesson One Page 4 So what are the SIMPLE MACHINES?

These SIMPLE MACHINES were already identified by the ancient Greeks. The Greeks understood the great power of SIMPLE MACHINES to help us do WORK.

He wrote about levers, screws and pulleys describing in mathematical terms their power as SIMPLE MACHINES. He had several important and useful inventions based on SIMPLE MACHINES.

4 Lesson One Page 4 So what are the SIMPLE MACHINES? Below we see the six types of SIMPLE MACHINES: inclined plane, wedge, lever, wheel and axle, and screw and an example of how we use each one in our everyday lives. These SIMPLE MACHINES were already identified by the ancient Greeks. The Greeks understood the great power of SIMPLE MACHINES to help us do WORK. Archimedes, the great scientist, engineer and mathematician of the ancient world was born c. 287 BC in Syracuse, Sicily. He wrote about levers, screws and pulleys describing in mathematical terms their power as SIMPLE MACHINES. He had several important and useful inventions based on SIMPLE MACHINES. Over the next few months we will study each of these SIMPLE MACHINES. Archimedes Today we will experiment with an INCLINED PLANE. Let s first learn more about INCLINED PLANES. An INCLINED PLANE is a flat sloping surface. Would you be able to lift the tractor into the truck? Your answer is probably NO. But what if you had to get the tractor into the truck, what could you do? You could try to find some really strong friends to help you out OR you could use a simple tool, the INCLINED PLANE. In the experiment we are going to do we will measure the WORK and FORCE needed to move a bag of peas or beans to the top of a stack of books.

5 Lesson One Page 5 INCLINED PLANE EXPERIMENT Purpose: Demonstrate and measure how an INCLINED PLANE makes WORK easier. Materials: books, ruler, calculator, bag of peas/beans, pencil, protractor, scissors, string, cutting board, and scale. Use the data table below to record your observations. Methods: Step One Measure the MASS of the peas/beans. Do this by weighing the bag on the scale. MASS of peas/beans = grams. PLEASE REMEMBER, WE ARE DOING A SCIENTIFIC EXPERIMENT AND IN SCIENCE WE MEASURE USING THE METRIC SYSTEM. Step Two Place four books on top of each other to make a tall pile. Place the cutting board on the edge of the books making an INCLINED PLANE. a. Measure the length of the INCLINED PLANE centimeters. b. Measure the angle of your INCLINED PLANE. Place the circular hole of the protractor where the cutting board meets the table surface. Write the degrees into the table. c. Place the bag of peas/beans in the cup of the scale. Place the scale under the cup. Make sure the cup is securely on the scale. Carefully and slowly push the bag and scale up the INCLINED PLANE. What is the reading on the scale? Write the number in the data table in the weight on scale column. Step Three Take two books away and repeat measuring the angle and pushing the bag and scale up the INCLINED PLANE. Write the number from the scale in the table. Step Four Take one book away, measure the angle and repeat pushing the bag and scale up the INCLINED PLANE made of one book. Write the number in the table. No inclined plane, just lifting Degrees of Angle 90 Weight on Scale (grams) INCLINED PLANE DATA TABLE Weight on Scale (kilograms)* Height of Books (centimeters) Height of Books (meters)** Force Work 4 books 2 books 1 book *divide grams by 1000 ** divide centimeters by 100 Did the amount of grams it took to push the bag up the INCLINED PLANE decrease as the angle of the plane decreased? Did it take less effort to push the bag up the INCLINE PLANE? So, what is going on?

6 Lesson One Page 6 Step Five Make a pile with two books and the inclined plane. Make another pile of four books behind the pile with two books. One partner holds a string at the base of the inclined plane while the other partner pulls the string to the top of the pile of four books. You may have to move the four book pile. String Inclined Plane 4 books 2 books How long is the string? centimeters Even though you need less FORCE to push the bag up to the height of four books, you have to push for a longer distance. Let s calculate WORK and fill in the last column of our table. What is the MASS of your bag of peas/beans? If we divide this by 1000 we will get the mass in kilograms. What is the MASS of your bag of peas/beans in kilograms? If we multiply the MASS of your bag of peas/beans by 9.8 (acceleration due to gravity), we can get the downward FORCE of gravity on your bag. kg x 9.8 = MASS of your bag acceleration due to gravity FORCE in Newtons We learned that WORK equals FORCE x distance. We need to multiply our FORCE by the height of the books. Newton x meter = Joules FORCE distance WORK Write this answer under the WORK column for the row showing the WORK for lifting up the bag. Now calculate the WORK done pulling up the bag for each of the INCLINED PLANES. Use the grams measured on the scale to calculate the FORCE. PROJECTS Do one of the following projects. You can also do a project which is your idea. 1. Learn about Archimedes and make a poster describing is ideas and inventions about Simple Machines. 2. Choose an ancient building or monument and learn about how Simple Machines were used to build them. Make a poster. Some ideas: the Egyptian pyramids, Maya pyramids, Stonehenge, Moai of Easter Island.

1 Work, Power, and Machines

CHAPTER 13 1 Work, Power, and Machines SECTION Work and Energy KEY IDEAS As you read this section, keep these questions in mind: What is work, and how is it measured? How are work and power related? How