Linear Motion

Linear Motion Today, we are talking about MOTION. The first definition is SPEED which is how fast you move.

Linear Motion Speed = ------------------ = ------------ Time T Distance D Speed = ------------------ = ------------ Time T Example 1) Speed = 60 miles / hour Example 2) Speed = 60 km / hour

Linear Motion D T Velocity – speed and direction To say something about constant velocity is to say the speedometer reading is staying the same and the compass reading is staying the same. D V = ----------- (average velocity) T

Linear Motion During middle school cross country practice, Mrs. Brooks’ average speed is 60 km/hr for 0.5 hours. How far has Mrs. Brooks traveled during practice? D = V t = (60 km/hr) (0.5 hr) = 30 km

Linear Motion The rate at which you change how fast is called ACCELERATION. Change in velocity Acceleration = ------------------------------- Time

Linear Motion As ___(name)____ and _____(name)____ race cars at 200 mi/hr, the cars do not accelerate. They are moving at CONSTANT speed or UNIFORM motion. If an object is not accelerating, the object must be at rest. NO!!! The object can have constant or UNIFORM motion.

Linear Motion If Coach D has a car that will go from 0 to 10 miles per hour in 10 seconds, what will be the car’s acceleration? (A = v/t) Coach D needs some new wheels! 1 mi/hr/s

Linear Motion If ____(name)_______ has a car that will go from 0 to 100 km/hr, what will be the car’s acceleration after 10 seconds? YA’ BOI!!! Or you GO Gur! Vf – Vi 100 – 0 A = -------------- = -------------- = 10 km/hr/s Tf – Ti 10 - 0

Linear Motion We have controls in the car tat can change ACCELERATION. What are these two controls in the car that cause a change in motion. GAS PEDDLE BRAKE

Linear Motion There is also one other control in the car that can cause a change in acceleration. What is the control and why does it cause a change? Steering wheel Changes the direction of the vehicle

Linear Motion Explain what happens to your body when you (a) accelerate the car, (b) decelerate the car, and © turn the steering wheel to change direction. Body goes back into the seat Body moves forward Body moves away from the direction of the turn

Linear Motion Suppose _____(name)_____ and _____(name)_____ are in an airplane, and they are moving 600 miles per hour. Can you detect that they are moving at all? If you are moving at constant motion with no change in acceleration, then you cannot detect or sense that they are moving at all. So we say that motion is relative.

Linear Motion For the ball being dropped, can you see the object gain speed? YES Freely falling objects will pick up a speed of 10 meters per second every second. A = 10 m/s2

Linear Motion Now, ____(name)_____ can say that the acceleration of freely falling objects is due to GRAVITY. We can substitute ‘g’ in for ‘a’ in the acceleration equation. V = at  V = gt V = (10 m/s2) (t) V = (10 m/s2) (10s) V = 100 m/s A freely falling object will have a speed of 100 m/s if it has 10 seconds to fall.

Linear Motion Q: How fast will an object fall if it falls for 5 seconds? V = a t = (10 m/s2)(5s) = 50 m/s

Linear Motion How much speed does the clay ball have after one second? V = at  gt = (10 m/s2) (1s) = 10 m/s

Linear Motion D = V t = (10 m/s) (1s) = 10 m/s Now, how far has the ball fallen after 1 second? D = V t = (10 m/s) (1s) = 10 m/s

Linear Motion Write down the distance equation to figure this out. Vi + Vf V (g)(t) D = ---------------- (t) = --------- (t) = ------------ (t) 2 2 2 Now, we have a relationship for how far something falls for an object that begins at rest. D = ½ gt2

Linear Motion Mr. _____(name 1)______ and Mr. _____(name 2)_____ walk up to a mine shaft and open the door. Mr. _____(name 1)______ opens the door up and says “Man, that’s musty!” Mr. ____(name 2)_____ is thinking, “I smelled something before the door was opened.” Now, Mr. _____(name 3)_____ walks up to the two of them. Being the smart one of the bunch, he is pondering, “What is the depth of the mine shaft? I have to know!!” If the time it takes for the ball to reach the bottom is 5 seconds, we can calculate the depth of the mine shaft using the distance equation above. What is the speed of impact at which the ball hits the ground after 3 seconds? V = g t = (10m/s) (3s) = 30 m/s How far did the object fall in 5 seconds? D = ½ gt2 = ½ (10)(5)2 = 125 m

Linear Motion If the object gains 10 m/s2 going down, then the object will decrease in speed going up. If ____(name)____ and ____(name)____ throw a baseball up at a velocity of 30 m/s, how much time will it take for the ball to reach the very top? 3 seconds

Linear Motion What is the total time the ball is in the air from when the ball leaves your hand to when it reaches the very top of its flight, to when it hits the ground? Why? 6 seconds (3 s up and 3 s down) The ball decelerates at 10 m/s2 going up and accelerates at 10 m/s2 going down due to gravity.

Linear Motion What’s the balls’ acceleration a split second just before it reaches the very top of its flight before it starts to come back down? 0 m/s2

Linear Motion Now, do this at your desk with a partner. Take a piece of paper and a book. Drop both items at the same time. Now, ball the piece of paper up and drop it at the same time. Then, put the paper under the book and drop them both at the same time. Finally, put the paper on top of the book and drop them at the same time. Lastly, place the piece of paper on top of the book and put the book on top of your partner’s head.