Slide 1 / 159 Slide 2 / 159 8th Grade Forces 2015-10-27 www.njctl.org Slide 3 / 159 Slide 4 / 159 Forces and Motion Click on the topic to go to that section · Motion Motion · Graphs of Motion · Forces · Newton's Laws of Motion · Newton's 3rd Law & Momentum Return to Table of Contents Slide 5 / 159 Slide 6 / 159 What does it mean to be in motion? What does it mean to be in motion? An object is in motion if it With a partner, come up changes position in with a scientific relation to a certain place, explanation of what it called a reference point. means if an object is in motion. Don't just say an Reference points are object is moving! places or objects used to determine the motion of an object. It is extremely important to choose reference points carefully.
Slide 7 / 159 Slide 8 / 159 Measuring Motion Relative Motion Motion is relative as it is dependent upon the reference point. Are you in motion right now? Think Speed is one of the many ways we measure motion. about it... Speed is a measure of the distance traveled per unit of time. That means you can find the speed of any object that is in motion! Are you in motion compared to your desk? Are you in motion compared to the sun? Slide 9 / 159 Slide 10 / 159 Finding Speed Finding Speed Discussion time! · What are some possible units to measure speed? Remember Speed = Distance ⁄ Time that speed= distance/time! · How do you think speed is measured when driving in a car? · How would you measure speed of an engine? For reference, and an animation of an internal combustion engine is shown below. We can rearrange the letters in the speed equation and solve for any of the other 2 pieces of information. Slide 11 / 159 Slide 11 (Answer) / 159 Units for Speed Units for Speed The SI unit for distance is meters (m) and for time is seconds (s). The SI unit for distance is meters (m) and for time is seconds (s). Given these units, what will be the SI unit for speed? (Hint: recall Given these units, what will be the SI unit for speed? (Hint: recall the speed equation speed= distance/time) the speed equation speed= distance/time) Answer meters/second which is usually shortened to m/s [This object is a pull tab]
Slide 12 / 159 Slide 12 (Answer) / 159 1 A snail travels a distance of 10 m in 6000 1 A snail travels a distance of 10 m in 6000 seconds. What is the snail's average speed? seconds. What is the snail's average speed? 60000 m/s 60000 m/s A A 0.02 m/s 0.02 m/s B B D Answer 600 m/s 600 m/s C C 0.002 m/s 0.002 m/s D D [This object is a pull tab] Slide 13 / 159 Slide 13 (Answer) / 159 2 A blimp travels at 3 m/s for 1500 s. What 2 A blimp travels at 3 m/s for 1500 s. What distance does the blimp cover in that time? distance does the blimp cover in that time? 500 m/s 500 m/s A A C 4500 m/s 4500 m/s Answer B B 4500 m 4500 m C C [This object is a pull 500 m 500 m tab] D D Slide 14 / 159 Slide 15 / 159 Speed When we talk about speed, it is important to know that there is a difference between instantaneous speed and average speed. Average speed can be calculated by dividing the total distance by the total time. This is what is usually calculated by runners in a race. Instantaneous speed is the speed of an object at any moment in time (an instant of time). Can you think of an example where you would use instantaneous time? Manipulate the speed of each car, solve for time, and predict which car will win!
Slide 16 / 159 Slide 17 / 159 Average vs Instantaneous Speed Average vs Instantaneous Speed Have you ever run a mile? Do you think you ran at the exact same It might take 3 hours to travel 300 km in a car. What would the speed the entire mile? average speed of the car be? Calculate it now. Think about Does that mean the car was going what runners that speed for the whole 3 hours of the trip? do at the very end of a When you go on a trip in the car, race. do you go the same speed the whole time? Talk to a partner about this. Slide 18 / 159 Slide 19 / 159 3 Your teacher times your mile run at 7.5 minutes, Average vs Instantaneous Speed that means your speed was 0.13 mile/min. Was this your average speed or your instantaneous speed? When you ride on the bus to school, does the bus driver travel at the same speed the entire trip? AAverage Speed School buses and other vehicles have BInstantaneous speedometers that Speed measure the speed of the vehicle at a specific moment in time. Do speedometers measure average speed or instantaneous speed? Slide 19 (Answer) / 159 Slide 20 / 159 3 Your teacher times your mile run at 7.5 minutes, 4 A student has built a model car that is designed to run at a constant speed. What should the student that means your speed was 0.13 mile/min. Was this your average speed or your instantaneous speed? measure to test whether the car runs at a constant speed, average or instantaneous speed? avg speed = AAverage Answer AAverage Speed Speed 1 mile/ 7.5 min = BInstantaneous 0.13 mile/min BInstantaneous Speed Speed [This object is a pull tab]
Slide 20 (Answer) / 159 Slide 21 / 159 4 A student has built a model car that is designed to 5 A swordfish travels for two hours. The first run at a constant speed. What should the student hour he covers 110 kilometers, and the measure to test whether the car runs at a constant second hour he covers 84 kilometers. What speed, average or instantaneous speed? is the average speed of the swordfish? A 110 km/h instantaneous AAverage Speed Answer Hint: Remember that speed B 84 km/h Average speed is total distance travelled divided BInstantaneous Speed by total time C 97 km/h [This object is a pull tab] D 194 km/h Slide 21 (Answer) / 159 Slide 22 / 159 6 A dog walks outside to go the bathroom every day. 5 A swordfish travels for two hours. The first On a given day, she walks 75 meters before she finds hour he covers 110 kilometers, and the a spot to use the bathroom. She walks at an average second hour he covers 84 kilometers. What speed of 2.5 meters per second. How long does it take is the average speed of the swordfish? her to find a place to use the bathroom? A 30 seconds A 110 km/h C Answer Hint: Remember that B 84 km/h B 2 minutes Average speed is total distance travelled divided by total time C 97 km/h C 188 seconds [This object is a pull tab] D 194 km/h D 90 seconds Slide 22 (Answer) / 159 Slide 23 / 159 6 A dog walks outside to go the bathroom every day. Velocity On a given day, she walks 75 meters before she finds a spot to use the bathroom. She walks at an average Velocity is another way to measure motion. Simply put, velocity speed of 2.5 meters per second. How long does it take is the speed of an object with a direction included . her to find a place to use the bathroom? A 30 seconds Runner's speed: 10 km/hr Runner's velocity: 10 km/hr to the East B 2 minutes Answer A C 188 seconds [This object is a pull D 90 seconds tab] What do you notice about the units for speed and velocity?
Slide 24 / 159 Slide 25 / 159 7 Carlos and Gina are riding on their horses to Why is velocity important? go into town. They travel 70 meters in 7 seconds going west. What is their velocity? Have you ever been in an airplane? Would would be the consequence of a pilot only knowing the speed of other nearby planes? A 490 m/s west B 10 m/s west C 490 m/s Tornadoes travel at about 170 km/h. Why is knowing the velocity of a D 10 m/s tornado important? Slide 25 (Answer) / 159 Slide 26 / 159 7 Carlos and Gina are riding on their horses to 8 A car travels 100 km/h west for 2 hours. The car go into town. They travel 70 meters in 7 seconds then travels 50 km/h east for one hour. What is the going west. What is their velocity? car's final position relative to its starting position? A 490 m/s west B 10 m/s west A 50 km west Hint: Find the distance Answer B and direction traveled for C 490 m/s B 150 km west each leg of the trip first. D 10 m/s C 250 km west Draw these distances on a number line using 0km D 50 km east [This object is a pull as the starting point. tab] Slide 26 (Answer) / 159 Slide 27 / 159 8 A car travels 100 km/h west for 2 hours. The car then travels 50 km/h east for one hour. What is the car's final position relative to its starting position? A 50 km west Answer B Hint: Find the distance Graphing Motion and direction traveled for B 150 km west each leg of the trip first. C 250 km west Draw these distances on [This object is a pull a number line using 0km tab] D 50 km east as the starting point. Return to Table of Contents
Recommend
More recommend
