GRAVITY Science – Physical World Unit Study Term

LEARNING INTENTIONS  To understand what gravity is and how it works.  To know the difference between gravity on earth and on the moon.  To recall what Galileo and Sir Isaac Newton discovered about gravity.  To learn about ways to defy gravity.

WHAT IS GRAVITY? ? ? ?

WHAT IS GRAVITY?  Gravity is a force that attracts objects together. On earth this force attracts everything to Earth. So no matter where you are on Earth all objects fall to the ground.

WHAT IS A FORCE? A force can make things Move faster Move slower Change direction Change shape

EXPERIMENT #1: HOW DOES GRAVITY WORK?

EXPERIMENT #1 Drop pairs of objects, one lot at a time while standing on a chair or desk. Your partner must look closely to see whether one object reached the floor before another or both objects reached the floor at the same time. You need to carefully record your results on your charts. ObjectVs.ObjectWhat dropped first? Cotton ballVs.Tissue paper BookVs.Vivid Block of woodVs.Glue stick Clearfile folderVs.1B5 Ball of paperVs.Sheet of paper PenVs.Colouring pencil SockVs.Shoe

THINKING ABOUT EXPERIMENT #1…  What would happen if you dropped a whole apple and half an apple at the same time from the same height: Would they hit the ground at the same time, or would one hit before the other?  WHY?

IMPORTANT TERMS TO KNOW… Mass The amount of matter in a given volume of something. Volume The amount of space that an object or substance takes up. Weight A measure of the force of gravity pulling on an object.

UNDERSTANDING MASS The mass of a bag of fluffy marshmallows is the same before -- and after -- a stampede of elephants changes its volume by squishing it to the size of a bar of soap.

WEIGHT VS. MASS Weight and mass are not the same. How much something weighs depends on how strongly gravity is pulling on it. So something will weigh less where the gravitational force on it is weaker (as on the Moon or in space, for example), even though its mass has not changed.

EXPERIMENT #2: HAMMER AND FEATHER What would happen if you dropped them simultaneously from the same height: Would they hit the ground at the same time or at different times? Video: Galileo on the Moon urce/phy03.sci.phys.mfw.galmoon/ urce/phy03.sci.phys.mfw.galmoon/

EARTH VS. MOON  The Earth is a very large object and it is also very heavy. This means that it has got a strong gravitational field. The moon is smaller than the Earth and is not as heavy.  Question: Is the moon’s gravity stronger or weaker than the Earth's gravity?

 Answer: Weaker. The moon's gravity is only 1/6th as strong as the Earth's. EARTH VS. MOON

THINKING ABOUT EXPERIMENT #2…  Did you expect the hammer and the feather to land on the surface of the Moon at the same time?  Why did the hammer and the feather fall at the same rate on the Moon but not on Earth?

GALILEO GALILEI: The man who dropped the balls. Galileo's _falling bodies_ experiment re-created at Pisa.flv

GALILEO GALILEI  Galileo Galilei was born near Pisa in  After studying at the University of Pisa, he was appointed to the chair of mathematics.  The theory which virtually everyone accepted at the time was the traditional theory of Aristotle, who believed that heavier objects fall more quickly than lighter ones.

GALILEO GALILEI  What the Leaning Tower of Pisa experiment demonstrates, is that Aristotle was wrong, that no matter what the difference in weight, two heavy objects will fall simultaneously at virtually the same speed.

SIR ISAAC NEWTON: The man who got a sore head. Famous Scientist - Sir Isaac Newton.mp4

SIR ISAAC NEWTON  Isaac Newton was born in England in  He was an English physicist, mathematician, astronomer, natural philosopher, alchemist and theologian, who has been considered by many to be the greatest and most influential scientist who ever lived.

SIR ISAAC NEWTON Newton himself often told the story that he was inspired to formulate his theory of gravitation by watching the fall of an apple from a tree. Although it has been said that the apple story is a myth, friends of Newton (such as William Stukeley), do in fact say it did happen, though not the cartoon version that the apple actually hit Newton's head.

SIR ISAAC NEWTON “Why should that apple always descend perpendicularly to the ground," he thought to himself. “Why should it not go sideways, or upwards? but constantly to the earths centre? Maybe the reason is, that the earth draws it. There must be a drawing power in matter.”

WHAT IS WEIGHTLESSNESS? ? ? ?

EXPERIMENT #3: WATER IN A CUP What would happen if you dropped a cup of water with holes in it? Would the water continue to pour out of the holes? Video: Weightlessness y03.sci.phys.mfw.zweightlessness/

THINKING ABOUT EXPERIMENT #2…  Were you surprised that the water stopped pouring out of the holes in the cup once the cup started to fall?  Can you think of a reason why this happened?

EXPERIMENT #4: SPINNING BUCKET Can you keep water inside a bucket if you turn it upside down?

EXPERIMENT #4… Materials you will need: Water Bucket with a handle A Strong Arm Steps: 1. Fill the bucket three quarters of the way with water. 2. Take the bucket by the handle and start spinning it around at your side from the ground, up to the sky, turning your arm behind you as the bucket makes it way back down towards the ground. 3. Keep the speed and motion of rotation the same. What happens? Does the water stay in the bucket or does it spill out of the bucket?

THINKING ABOUT EXPERIMENT #4… If you keep the speed up and a smooth motion of the rotation going around with your arm, the water will stay inside the bucket. WHY? Because the force of gravity pulling the water towards the center of the earth as the bucket heads down and as the bucket of water goes up towards the sky the motion of the water is forced to stay inside the bucket (the wall and bottom) as it can not escape from inside the bucket.

EXPERIMENT #5: DON’T CRACK THE EGG! With 10 pieces of paper, 10 straws and some tape can you save your precious eggs?!

THINKING ABOUT EXPERIMENT #5…  Which designs didn’t work? Why?  Which design did work?

DEFYING GRAVITY IN YOUR OWN HOME What if you lived in space?

DEFYING GRAVITY IN YOUR OWN HOME It may not be long before humans are able to live for a long time in outer space—not just astronauts, but families. Imagine your own home is going to be transported to an orbit around Earth…  Design a room that could exist in a microgravity environment in outer space.

DEFYING GRAVITY IN YOUR OWN HOME  Think about… How will you prevent food from floating up off kitchen plates? How will you stay in bed while sleeping?

LET’S RE-CAP… WHAT is gravity? HOW does gravity work? WHAT is the difference between ‘weight’ and ‘mass’? WHY is the strength of gravity different on the moon? WHAT did Galileo discover? WHAT did Sir Isaac Newton discover?

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