Aristotles idea of motion Aristotle believed that a

Aristotle’s idea of motion Aristotle believed that a stone fell to the ground because the stone and the ground were similar in substance (in terms of the 4 basic elements, they were mostly "earth"). Likewise, smoke rose away from the Earth because in terms of the 4 basic elements it was primarily air (and some fire), and therefore the smoke wished to be closer to air and further away from earth and water. Aristotle also argued that the manner in which a body falls does depend on it weight i. e. a 2 kg block of iron will faster than a 1 kg block of iron. Is Aristotle correct?

Galileo’s Pisa Experiment

Motion We looked at how Galileo showed through experimentation that Aristotle was wrong about heavy objects falling faster than lighter objects. Now we are going to look at Aristotle’s idea that force was needed to keep an object moving.

Galileo’s Concept of Inertia On a downward slope, the speed increased On an upward slope, the speed decreased When there is no slope, the speed didn’t change

Galileo’s Concept of Inertia A ball rolling down an incline on the left tends to roll up to its same height on the right What is the final position for this ball?

Galileo’s Concept of Inertia These experiments showed Galileo was that a force is needed to get an object to start moving but that the object will keep moving until another force stops it. The force that often stops objects in friction.

Galileo’s Concept of Inertia He summed this up by saying that objects at rest tend to stay at rest and object in motion, stay in motion. The property of objects to maintain their state of motion is inertia.

Inertia Demonstration http: //www. youtube. com/watch? v= X 0 OCLRb. Qzzs ¡ Activity ¡

What is Mass? When we want to apply to force to an object to get it moving, how do we figure out how much force we need? The amount of force needed depends on the amount of matter that the object has. Mass is a measure of the inertia in an object!

Mass – A Measure of Inertia ¡ Does this make sense?

Mass vs. Weight We often think about mass and weight as being the same, but they are not! Mass is a measure of the amount of matter in an object. It does not depend on gravity. The mass of an object is the same on Earth and on the Moon.

Mass vs. Weight does depend on gravity. Your weight on the Moon would be much less than here on Earth because there is less gravity! Weight is a measure of the force of gravity on an object ¡ Mass and weight are proportional ¡ We measure mass in Kilograms

Mass vs. Weight Questions to think about: If you have a heavy iron dumbbell out in space, what would its mass be? It’s weight? Would it be easy for an astronaut to shake the dumbbell?

Mass vs. Volume Think about a big, fluffy pillow and a small car battery… Which has more mass? Which has more volume? Volume is measures in liters or cubic meters *Remember 1 ml = 1 cubic centimeter

Density is a measure of how much matter is in a given volume Density = mass volume

Density is the “lightness” or “heaviness” of material, just like mass, but it also depends on the amount of space that the matter is taking up (volume)

How do we measure density? If we know the mass and we know the volume, we can calculate the density. You can also measure density by water displacement. (Activity)

Finding the Density of Rubber Lab notebooks: ¡ Title: What is the density of rubber? ¡ Materials: ¡ l l l Graduated cylinder 4 sizes of rubber Beaker of water Triple beam balance or electronic balance Ruler

Finding the Density of Rubber You will find the density of rubber by method of water displacement. ¡ First find the mass of each rubber ¡ 2 nd Fill the grad. Cylinder with water and measure the volume. (initial vol) ¡ Add the rubber and read the water volume. (final volume) ¡ Subtract the final volume with initial volume to get the volume of the rubber. ¡

Finding the Density of rubber ¡ Data table Rubber size Mass (grams) Volume (ml) #2 #3 #5 #6 ¡ Graphing Chart: mass Obtain the Density By getting slope of line volume Y=mx or m = mass/volume

Finding the Density of rubber ¡ Analysis: l l l What is the density of rubber? Why does size not matter in obtaining the density of the rubber? How will the density of a substance be different if we calculated with weight instead of mass?

How do we measure density? You can compare density of liquids by seeing which floats on top Material Density Rubbing Alcohol. 79 Lamp Oil. 80 Baby Oil. 83 Vegetable Oil. 92 Ice Cube. 92 Water 1. 00 Milk 1. 03 Dawn Dish Soap 1. 06 Light Corn Syrup 1. 33 Maple Syrup 1. 37 Honey 1. 42

How are you feeling about this concept? ¡ Reflection