Matter, Force, Energy, Motion, and the Nature of Science (NOS) Elementary SCIEnCE Dr. Suzanne Donnelly Longwood University donnellysm@longwood.edu
Day 3: Morning schedule Problem-Based Learning (PBL) What it means to be matter Classifying matter Pendulum activity Forces and motion Lunch
Problem-based Learning (PBL) Take it away, Patti! J
What is matter? Remember the two properties that define matter It has mass It takes up space (has volume)
How do we classify matter? Is a liquid more like a solid or a gas?
Case study: states of matter Read the following article about modeling the states of matter in a first grade classroom How can you bring modeling into your classroom?
Matter and its properties It may seem simple, but the fact that all matter has mass and takes up space defines much of the ways we observe that matter behaves Pendulum inquiry
Prove it! We tell our students that matter has mass and takes up space, and that everything we see around us is matter but what do we do to prove it to them? In groups develop a representation suitable for elementary learners that matter has mass and takes up space using everyday household objects
Day 3: Afternoon Schedule Forces and motion Linear motion and The Macarena Forces, Projectile Motion, and rockets Energy Adjourn
Refresher on forces Force is a push or pull on an object Evidence of a forces acting on on an object Change in the motion of the object Change in the shape of the object (deformation) A force on an object does not always change its motion, but it always changes the shape of the object, even if it isn t visible to the naked eye Forces are measured in the unit of the Newton (N) in science Forces and motion are critical science topics covered by the science SOLs in 1 st, 3 rd, and 4 th grade
Some stats on forces Forces have magnitude (big/small ) and direction (left/right/up/down ) Forces are represented with arrows The length of the arrow represents the magnitude, the arrow head represents the direction of the force
Equilibrium and forces If an object is not undergoing a change in motion, then it is said to be in mechanical equilibrium Consider a spring scale holding a bag of flour What forces are acting on the flour as it is suspended? Tension on the spring (upward) Weight of the flour (downward)
Objects at rest on surfaces When an object is at rest on a surface, its weight exerts a downward force on it And the surface exerts an equal and opposite force on the object (an upward force equal in magnitude to the object s weight) This support force is called the normal force The upward arrow represents the Normal Force Net force = 0 when an object is at rest
Objects in motion on surfaces When an object is in motion on a surface, its weight exerts a downward force on it and the surface exerts an equal and opposite normal force on the surface There is also a force of motion (a push or pull causing the object to move), as well as the force of friction, which opposes the object s motion Force of friction Force of motion Net force does not have to be zero if an object is moving and changing speed!
Speed Before Galileo, people just described motion as slow or fast Galileo was the first to measure speed by comparing distance traveled to the amount of time it took an object to move that distance Speed = distance/time
Velocity When we know both the speed and the direction of an object, we know its velocity For example, if we know that a car is driving at 45 miles per hours, we just know its speed But if we know the car is driving 45 miles per hour due north, we know its speed and its direction
Constant velocity Constant speed just means that the object isn t speeding up or slowing down Constant velocity means that the object has a constant speed and it s not changing direction This means that the path the object is traveling doesn t curve it s a straight line One of these graphs shows an object traveling at a much higher speed than the other which one?
Acceleration Think about a ball rolling down a hill Does its speed remain constant as it rolls, or does it change?
Acceleration as a change in velocity Any time an object s velocity changes, it is undergoing acceleration Acceleration = (change in velocity)/(change in time) When an object speeds up, we say it is accelerating When an object slows down, we say it is decelerating
What does acceleration mean? Suppose you are driving at a speed of 35 km/hr If you press the gas pedal with a certain force, you know that you can increase your speed by 5 km/hr in every second So, after 1 second, you will be going 40 km/hr After 2 seconds, you will be going 45 km/ hr, etc. Your acceleration = change in velocity/ change in time Acceleration = (5 km/hr)/(1 second)
Another kind of acceleration An object can be accelerating even if its speed doesn t change How?
Linear motion inquiry Use the motion detectors to complete the activities to help you explore linear motion
Acceleration and free fall When an object is falling and there is no air resistance, it is said to be in free fall An object in free fall on Earth will accelerate (increase its velocity as it falls towards Earth )at a rate of 9.8 m/s 2
Inquiry: replicating one of Galileo s experiments What do you think happens if you drop two balls with the same shape but different masses from the same height?
Extending Galileo s experiments What would happen if you dropped a book and a feather at the same time? Apollo 15 confirmed Galileo s prediction that any two objects will hit the ground at the same time (regardless of their masses) if there is no air resistance http://nssdc.gsfc.nasa.gov/planetary/lunar/ apollo_15_feather_drop.html
What is weight? Weight is a force it is the measurement of the force of attraction between an object and the Earth Because it is a force, weight is measured in Newtons A weight of 1 N is approximately the weight of an apple When objects are falling, they may become weightless, but they will NOT become massless Weight can change depending upon your location, but mass will ALWAYS stay the same! Relating mass and weight: Funded 1 through kg 2013 weighs Mathematics and Science 9.8 Partnership Newtons Grant, Elementary SCIEnCE
Comparing weights on Earth and other places The weight of an object on the moon is about 1/6 of its weight on Earth because the moon is so much smaller than the Earth, and thus exerts less of a gravitational force on objects If an elephant weighs 98,000 N on Earth, what does it weigh on the moon?
Weightlessness You don t need to take your students to outer space to demonstrate weightlessness!
Why do students confuse mass and weight? What does a scale measure?
Projectile motion Without gravity, you could throw a rock at an angle towards the sky and it would keep going in a straight line at that angle Because of gravity, its path curves Any object that is projected by some means (throw, cannon shooting it, toss, etc.) and continues by its own inertia is called a projectile v = x/t
Curved path of projectiles launched horizontally If an object is just dropped, its motion will only be vertical The curved path of projectiles is the result of the combination of vertical and horizontal motion (just like we talked about with vectors) Their combined effect is that produces the parabolic trajectory of a projectile
Example: a cannon
Velocity of a projectile The velocity of a projectile changes throughout its trajectory because its vertical component changes Its horizontal component is the same everywhere The path of the projectile changes a bit depending upon whether there is air resistance The greater the angle the projectile is launched at (this angle, θ, can be up to 90 degrees), the higher the projectile will fly
If we neglect air resistance The speed lost by a projectile going upwards will equal the speed gained as the projectile comes down So, the time going up will equal the time coming down At the top of the trajectory, the speed of the object is zero The range of the object is how far the projectile lands from where it was launched from Range depends upon the angle the projectile is launched from The angle (θ) with respect to the ground that will produce the largest range is 45 degrees Range = v i 2 sin 2 g ( θ )
Rockets! Let s get outside and launch some rockets! You will each be launching the rockets at different angles, so some of the rockets will soar higher, while some will have a greater range You will each be getting a rocket and a launchpad to take back to your classroom
Energy and rockets What types of energy do you think we observed while launching those rockets?