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Transcript
Science 10/7/15 Force and Motion Day #1 • >Pick up the “Force and Motion” Concept Review from the cart and write your name on it! • >Clear your desk and get ready to learn some new concepts! • The learning objective for today is to learn the vocabulary necessary for tomorrow’s outside activity. Forces and Motion Terms and vocabulary Review Concepts What is motion? • Motion is a change in position. • An object changes position if it moves relative to a reference point. Reference Point Distance • Distance is the length of the route you travel. Starting Point To find the distance I’ve traveled, I measure my path from my starting point to my ending point. Ending Point Distance • Distance is the length of the route you travel. Starting Point 150 meters To find the distance I’ve traveled, I measure my path from my starting point to my ending point. 50 meters Ending Point Distance • Distance is the length of the route you travel. Starting Point 150 meters Displacement 10 cm SE To find the distance I’ve traveled, I measure my path from my starting point to my ending point. 50 meters Total Distance=200 meters Ending Point Displacement • Displacement is the difference in position between your starting point and your ending point. It has a direction. • What is the displacement here? Displacement • Displacement is the difference in position between your starting point and your ending point. It has a direction. • What is the displacement here? 200 m 75 m 75 m 200 m • My displacement would be 0 m because I started and ended at the same spot. • My distance would be the length of the path that I traveled. The distance is 550 m. • You are a truck driver. If you were getting paid by the mile for your travel, would you rather have your distance or your displacement measured for round trips? Explain….. • My displacement would be 0 m because I started and ended at the same spot. • My distance would be the length of the path that I traveled. The distance is 550 m. • You are a truck driver. If you were getting paid by the mile for your travel, would you rather have your distance or your displacement measured for round trips? Explain….. You would rather be paid by your distance travelled, it is always at least as far as the displacement. How would you measure displacement here? How would you measure distance? Distance=total length travelled Displacement=distance from the beginning point to the end point. Use your ruler to measure on your paper now. How would you measure displacement here? How would you measure distance? Distance=total length travelled = 13.5 cm Displacement=distance from the beginning point to the end point. 10 cm 8.5 cm 8.5 cm + 5 cm = 13.5 cm How would you measure displacement here? How would you measure distance? 5 cm Measure the distance and displacement for this example in centimeters. One centimeter = 1 mile Measure the distance and displacement for this example in centimeters. One centimeter = 1 mile 10 cm 11 cm 10 cm 10 cm + 11 cm + 10 cm= 31 cm or 31 miles Speed • Speed is how fast something is moving. • Speed = Distance divided by Time • Try these: 1. What is the speed of a car that has traveled 300 miles between the hours of 5:00 P.M. and 9:00 P.M.? 2. Drew drove from Wauconda to Crystal Lake in 25 minutes. He traveled a total of 10 miles to his destination. What was his average speed? Speed • Speed is how fast something is moving. • Speed = Distance divided by Time • Try these: 1. What is the speed of a car that has traveled 300 miles between the hours of 5:00 P.M. and 9:00 P.M.? 300 miles / 4 hours= 75mph 2. Drew drove from Wauconda to Crystal Lake in 25 minutes. He traveled a total of 10 miles to his destination. What was his average speed? 10 miles / 25 minutes= .4 miles/min. Average Speed Vs. Instantaneous Speed • What is the difference between these two types of speed? Give an example…. Average Speed Vs. Instantaneous Speed • What is the difference between these two types of speed? Give an example…. Average speed =the runners ran 100 meters in 10 seconds or 10 m/s average Instantaneous Speed= The bullet cut through the apples at a speed of 5,000 m/s Constant Speed •? Constant Speed • Your cruise control on your car allows you to drive at a constant speed. It stays the same over time. Were you right? • Instantaneous speed is your speed at any given moment in time. • Average speed is the average of your speed over a certain distance. 1. When a police officer pulls your dad or mom over for speeding, is he measuring instantaneous speed or average speed? Were you right? • Instantaneous speed is your speed at any given moment in time. • Average speed is the average of your speed over a certain distance. 1. When a police officer pulls your dad or mom over for speeding, is he measuring instantaneous speed or average speed? >Instantaneous Speed: It is how fast your dad was going the instant that he clocked him with the “radar gun”. Graphing • If you are given the following information, could you graph it? Let’s try….. • You need: – – – – – Title Time(horizontal axis) Distance(vertical axis) Units Spread out your numbers Distance (M) Time (Sec) 0M 0 Sec 30 M 1 Sec 60 M 2 Sec 100 M 5 Sec Average Speed (Distance vs Time) Velocity Vs. Speed • What is the difference between velocity and speed? • What do they have in common? Velocity Vs. Speed • What is the difference between velocity and speed? One has direction (velocity) • What do they have in common? speed • Both velocity and speed are how fast an object is moving. • The difference is that velocity also has a direction. • For example, my speed is 50 m/s. • My velocity is 50 m/s north. Acceleration • Acceleration is your change in velocity divided by the time it takes for the change to occur. • (final speed – initial speed) • time • What would be my car’s acceleration if its final speed was 50 MPH and its initial speed was 2 MPH over 6 seconds? Acceleration • Acceleration is your change in velocity divided by the time it takes for the change to occur. • (final speed – initial speed) • time • What would be my car’s acceleration if its final speed was 50 MPH and its initial speed was 2 MPH over 6 seconds? Acceleration • Acceleration is your change in velocity divided by the time it takes for the change to occur. • (final speed – initial speed) • time • What would be my car’s acceleration if its final speed was 50 MPH and its initial speed was 2 MPH over 6 seconds? 50 MPH - 2 MPH / 6 seconds= 8 MPH / sec /sec Types of Acceleration • There are three types of acceleration: – Speeding up – Slowing down – Changing Direction Positive and Negative Acceleration • Positive acceleration occurs when you are speeding up. • Negative acceleration occurs when you are slowing down. Mass, Momentum, and Inertia What are they? • Mass is the amount of matter in an object. Which would have more mass, a cotton ball or a lead ball the same size? The lead ball • An object that is small may have more mass than an object that is bigger. It just depends on what it is made of. • Inertia is the tendency of an object to resist a change in its motion. • The more mass an object has, the harder to speed it up, slow it down, or turn it. It has more inertia. Momentum • Momentum is a measure of how hard it is to stop an object. • Momentum is calculated: Mass X Velocity What is the momentum of a car with a mass of 30,000 KG and a velocity of 10 kilometers per hour? What are the units? Conservation of Momentum • The total momentum of objects that collide with each other is the same before and after the collision. • What lab did we do showed this? • What happened? • How is this principle applied to bowling, billiards, etc.? Newton’s First Law • What is Newton’s First Law? If there is no net force acting on an object, the object remains at rest. If the object is moving, it continues to move in a straight line with constant speed unless acted upon by a force. What are some examples that show this? Newton’s Second Law • What is Newton’s Second Law? Acceleration of an object depends on the force that is applied to an object How does this law relate to sports you know? Newton’s Third Law • What is Newton’s Third Law? For every action, there is an opposite and equal reaction What are some examples of this? Friction What are the three types of friction? • Static friction: the type of friction that prevents an object from moving when a force is applied • Rolling friction: the type of friction that helps a wheel turn and keeps the tire from slipping on the ground • Sliding friction: the type of friction that slows down an object that slides What are some examples of each in sports? Forces That Act on Objects • Gravity: the force that acts between any two objects that have mass • Friction: ??? • Air Resistance: a form of friction that acts to slow down any object moving in the air Force • Force is measured in newtons (N). • We use a spring scale to measure newtons. When did we do that? Catapults/Trebuchets • You need to be able to identify the following parts: throwing arm frame base projectile counterweight axle arm rubber band projectile cup release angle Counterweight arm sling Let’s see what you can do…… Catapults and Trebuchets