Motion-Physics Notes-PDF

Objective: Motion Physics Dr. Rex Motion In order to measure motion you need a reference poin...

Objective: Motion Physics Dr. Rex Motion In order to measure motion you need a reference point! Reference Point: An object at rest that is used to judge the motion of another object. Wednesday, July 15, 15  Objective: Motion Physics Dr. Rex Motion Motion: When an object changes position with respect to a reference point. Wednesday, July 15, 15  Objective: Motion Physics Dr. Rex Motion An object in motion travels a certain distance in a certain amount of time. 30 m 1 min Wednesday, July 15, 15  Objective: Motion Physics Dr. Rex Speed Speed: The rate at which an object moves. 30 m Text 1 min Wednesday, July 15, 15  Objective: Motion Physics Dr. Rex Speed distance Speed = time Speed is measured in: “/” is read “per” mi/hr It means “divided m/s by”. Wednesday, July 15, 15  Objective: Motion Physics Dr. Rex Speed Usually we are talking about average speed. Average speed: How fast a total distance is covered. total distance Average Speed = total time Wednesday, July 15, 15  Objective: Motion Physics Dr. Rex Speed Mouse............................................3 m/s Wednesday, July 15, 15  Objective: Motion Physics Dr. Rex Speed Usain Bolt............................................10 m/s Wednesday, July 15, 15  Objective: Motion Physics Dr. Rex Speed Cheetah............................................30 m/s Wednesday, July 15, 15  Objective: Motion Physics Dr. Rex Speed Sound............................................343 m/s Wednesday, July 15, 15  Objective: Motion Physics Dr. Rex Speed Space Shuttle............................10,000 m/s Wednesday, July 15, 15  Objective: Motion Physics Dr. Rex Speed Sometimes we discuss instantaneous speed. Instantaneous speed: An object’s speed at one instant. Instantaneous speed is what the car speedometer shows you. Wednesday, July 15, 15  Objective: Motion Physics Dr. Rex Speed Constant speed means that the speed is not changing. 30 mi/hr 30 mi/hr 30 mi/hr If an object has constant speed then average speed = instantaneous speed Wednesday, July 15, 15  Objective: Motion Physics Dr. Rex Speed Mouse............................................3 m/s Wednesday, July 15, 15  Objective: Motion Physics Dr. Rex Speed Usain Bolt............................................10 m/s Wednesday, July 15, 15  Objective: Motion Physics Dr. Rex Speed Cheetah............................................30 m/s Wednesday, July 15, 15  Objective: Motion Physics Dr. Rex Speed Sound............................................343 m/s Wednesday, July 15, 15  Objective: Motion Physics Dr. Rex Speed Space Shuttle............................10,000 m/s Wednesday, July 15, 15  Objective: Motion Physics Dr. Rex Speed Tucson Flagstaff 400 distance traveled 300 every hour Distance (km) 200 average speed 100 0 0 1 2 3 4 Time (hours) Wednesday, July 15, 15  Objective: Motion Physics Dr. Rex Class Work! 1. A jogger runs 5 miles in 1 hour. What is his average speed? 2. A jogger runs 5 miles in 1 hour and then walks 2 miles in 1 hour. What is his average speed? Wednesday, July 15, 15  Objective: Motion Physics Dr. Rex Speed --other forms! Distance Speed = Time Distance Time = Speed Distance = Speed x Time Wednesday, July 15, 15  Objective: Motion Physics Dr. Rex Class Work! 1. If a car is traveling at an average speed of 110 km/hr, how long will it take to travel 715 km? 2. If a train is traveling at an average speed of 150 km/hr, how far will it travel in 4 hours? Wednesday, July 15, 15  Objective: Motion Physics Dr. Rex Distance Distance (d): How much ground an object has covered during its motion. Wednesday, July 15, 15  Objective: Motion Physics Dr. Rex Distance What is the total distance traveled if a lizard moves from... 1. 0 to 10? 2. 0 to 10 and back to 0? 3. 10 to 5? x 4. 5 to 10? Wednesday, July 15, 15  Objective: Motion Physics Dr. Rex Distance The direction does not matter for distance! Wednesday, July 15, 15  Objective: Motion Physics Dr. Rex Displacement Displacement (∆x) : How far out of place an object is. Wednesday, July 15, 15  Objective: Motion Physics Dr. Rex Displacement Displacement (∆x) : The difference bet ween an object’s initial position and its final position. ∆x = x final - x initial Wednesday, July 15, 15  Objective: Motion Physics Dr. Rex Displacement Position (x) : The point in space occupied by an object. Wednesday, July 15, 15  Objective: Motion Physics Dr. Rex Displacement What is ∆ x if a lizard moves from... 1. 5 to 10? 2. 10 to 5? 3. - 10 to - 5? x Wednesday, July 15, 15  Objective: Motion Physics Dr. Rex Displacement The direction does matter for displacement! 4m right 2m up 2 m down 4m left Wednesday, July 15, 15  Objective: Motion Physics Dr. Rex Scalars and Vectors Scalar: A physical quantity that does not include direction. What is the distance? Wednesday, July 15, 15  Objective: Motion Physics Dr. Rex Scalars and Vectors Vector: A physical quantity that does include direction. What is the displacement? Wednesday, July 15, 15  Objective: Motion Physics Dr. Rex Velocity A Puzzle: 2 hang-gliders leave the same hill at the same time. They both fly at 20 km/h for 30 minutes and then 50 km/h for one hour. Why don’t they end up at the same place? Wednesday, July 15, 15  Objective: Motion Physics Dr. Rex Velocity A Puzzle: 2 hang-gliders leave the same hill at the same time. They both fly at 20 km/h for 30 minutes and then 50 km/h for one hour. Why don’t they end up at the same place? They went in different directions!! Wednesday, July 15, 15  Objective: Motion Physics Dr. Rex Velocity Velocity is speed and direction! Speed might be similar, but velocity is different when cars travel in different directions! Wednesday, July 15, 15  Objective: Motion Physics Dr. Rex Velocity Velocity: Rate of change of an object’s position. Velocity includes direction! 30 km/hr for ward Wednesday, July 15, 15  Objective: Motion Physics Dr. Rex Velocity Velocity: Rate of change of an object’s position. Velocity includes direction! 30 km/hr backward Wednesday, July 15, 15  Objective: Motion Physics Dr. Rex Velocity Velocity changes when speed changes or when direction changes. Constant velocity can only happen along a straight line! Wednesday, July 15, 15  Objective: Motion Physics Dr. Rex Class Work! 1. If a plane is flying at a constant speed, does that mean it also has a constant velocity? 2. If a plane is flying at a constant velocity, does that mean it also has a constant speed? Wednesday, July 15, 15  Objective: Motion Physics Dr. Rex Velocity displacement Velocity = time Velocity is measured in: “/” is read “per” mi/hr It means “divided m/s by”. Wednesday, July 15, 15  Objective: Motion Physics Dr. Rex Velocity Velocity: Specifically...how fast position changes. ∆x Velocity = ∆t x final - x Initial Velocity = Time Wednesday, July 15, 15  Objective: Motion Physics Dr. Rex Resultant Velocity Resultant Velocity: When we combine 2 velocities! When velocities are in the same direction: Add them together to get resultant velocity. Wednesday, July 15, 15  Objective: Motion Physics Dr. Rex Resultant Velocity Resultant Velocity: When we combine 2 velocities! Walkway moving: 2 m/s left 1 m/s Pilot walking: 1 m/s left Resultant Velocity: 2 m/s Wednesday, July 15, 15  Objective: Motion Physics Dr. Rex Resultant Velocity Resultant Velocity: When we combine 2 velocities! Walkway moving: 2 m/s left 1 m/s Pilot walking: 1 m/s left Resultant Velocity: 2 m/s 3 m/s left Wednesday, July 15, 15  Objective: Motion Physics Dr. Rex Resultant Velocity Resultant Velocity: When we combine 2 velocities! When velocities are in the opposite direction: Subtract them to get resultant velocity. Wednesday, July 15, 15  Objective: Motion Physics Dr. Rex Resultant Velocity Resultant Velocity: When we combine 2 velocities! Treadmill moving: 1 m/s left Woman walking: 1 m/s right 1 m/s Resultant Velocity: 1 m/s Wednesday, July 15, 15  Objective: Motion Physics Dr. Rex Resultant Velocity Resultant Velocity: When we combine 2 velocities! Treadmill moving: 1 m/s left Woman walking: 1 m/s right 1 m/s Resultant Velocity: 0 m/s any direction! 1 m/s Wednesday, July 15, 15  Objective: Motion Physics Dr. Rex Resultant Velocity Resultant Velocity: When we combine 2 velocities! Walkway moving: 2 m/s right 1 m/s Pilot walking: 1 m/s left Resultant Velocity: 2 m/s Wednesday, July 15, 15  Objective: Motion Physics Dr. Rex Resultant Velocity Resultant Velocity: When we combine 2 velocities! Walkway moving: 2 m/s right 1 m/s Pilot walking: 1 m/s left Resultant Velocity: 2 m/s 1 m/s right Wednesday, July 15, 15  Objective: Motion Physics Dr. Rex Resultant Velocity Resultant Velocity: When we combine 2 velocities! When velocities are in the opposite direction: Subtract the smaller number from the larger. 1 m/s The resultant velocity is in the direction of 2 m/s the larger velocity. Wednesday, July 15, 15  Objective: Motion Physics Dr. Rex Class Work! 1. You are on a train going east at 35 m/s. You stand up and walk down the aisle east at 1 m/s. What is your resultant velocity? 2. You are on a train going east at 35 m/s. You stand up and walk down the aisle west at 1 m/s. What is your resultant velocity? Wednesday, July 15, 15  Objective: Motion Physics Dr. Rex Acceleration TRUE or FALSE... When you speed up on your unicycle you are accelerating. When you slow down on your unicycle you are accelerating. As long as you maintain a constant speed on your unicycle you never accelerate. Wednesday, July 15, 15  Objective: Motion Physics Dr. Rex Acceleration Velocity: Rate of change of an object’s position. Acceleration: Rate of change of an object’s velocity. What are three ways to change velocity? What are three ways to accelerate? Wednesday, July 15, 15  Objective: Motion Physics Dr. Rex Acceleration Velocity: Rate of change of an object’s position. Acceleration: Rate of change of an object’s velocity. ++ Speed is increasing for ward= positive acceleration ++ Wednesday, July 15, 15  Objective: Motion Physics Dr. Rex Acceleration Velocity: Rate of change of an object’s position. Acceleration: Rate of change of an object’s velocity. Direction is changing. Wednesday, July 15, 15  Objective: Motion Physics Dr. Rex Acceleration Velocity: Rate of change of an object’s position. Acceleration: Rate of change of an object’s velocity. -- Speed is decreasing for ward = negative acceleration -- Wednesday, July 15, 15  Objective: Motion Physics Dr. Rex Class Work! How is velocity changing? 1. A plane taking off 2. A tomato smashing into a wall 3. Jogging on a winding trail 4. A windup toy running down Wednesday, July 15, 15  Objective: Motion Physics Dr. Rex Acceleration Velocity: Specifically...how fast position changes. Acceleration: Specifically...how fast velocity changes. ∆ Velocity Acceleration = ∆ Time Final velocity-Initial velocity Acceleration = Final Time - Initial time Wednesday, July 15, 15  Objective: Motion Physics Dr. Rex Acceleration Final velocity-Initial velocity Acceleration = ∆ Time Acceleration is measured in: “/” is read “per” m/s/s It means “divided OR by”. m/s2 Wednesday, July 15, 15  Objective: Motion Physics Dr. Rex Acceleration 3s 2s 1s 0s 3 m/s 2 m/s 1 m/s 0 m/s 3 m/s - 0m/s Acceleration = = 1 m/s/s left 3s Wednesday, July 15, 15  Objective: Motion Physics Dr. Rex Class Work! B A 1. A plane passes point A going 8,000 m/s north. 40 seconds later it passes point B going 10,000 m/s north. What was the plane’s acceleration from A to B? Wednesday, July 15, 15  Objective: Motion Physics Dr. Rex Class Work! 2. A coconut falls from the top of a tree and reaches a velocity of 19.6 m/s when it hits the ground. It takes 2 s to reach the ground. What is the coconut’s acceleration? Wednesday, July 15, 15  Objective: Motion Physics Dr. Rex Class Work! What’s happening? 50 Velocity (m/s) 38 25 13 0 0 1 2 3 4 5 Time (seconds) Wednesday, July 15, 15  Objective: Motion Physics Dr. Rex Class Work! What’s happening? 50 Velocity (m/s) 38 25 13 0 0 1 2 3 4 5 Time (seconds) Wednesday, July 15, 15  Objective: Motion Physics Dr. Rex Class Work! What’s happening? 50 Velocity (m/s) 38 25 13 0 0 1 2 3 4 5 Time (seconds) Wednesday, July 15, 15  Objective: Motion Physics Dr. Rex Class Work! What’s happening? 50 Velocity (m/s) 38 25 13 0 0 1 2 3 4 5 Time (seconds) Wednesday, July 15, 15