1 PHYSICS MR BALDWIN Speed & Velocity 9/15/2014 AIM: What is motion and how does it change?DO NOW: What do you understand about the terms speed and acceleration?Home Work:
2 Laws of Motion Everything in the universe is in nonstop motion. Motion is the rule, not the exception.The laws which govern the motion of atoms and stars apply to the motion in our everyday lives.
3 Distance and Displacement Distinction between distance and displacement.Distance traveled (dashed line) is a measure of length along the actual path.Displacement (blue line) is how far the object is from its starting point, regardless of how it got there.
4 Speed & Velocity Speed: time rate of change of distance : how far an object travels in a given time intervalVelocity includes directional information: time rate of change of displacement
5 Average Speed & Instantaneous Speed The instantaneous speed is the speed as given on your speedometer. The speed at that instant.Speed given by the speedometerThe average speed is the total distance traveled by an object divided by the total time taken to travel that distance.CHECK: Determine the unitsUnit: m/s; km/h; mph
6 CHECK: Can you write other forms of the equation to determine the other two quantities t & d?
7 Problem Solving Technique: G.U.S.S. Givens; Unknown; Substitute & SolveWrite out your Givens.Identify your Unknown.Check for unit consistency. If not…convert!Substitute into equation (with units)Find an equation relating quantities.Solve for unknown.
8 QUIZ CHECK. What is the average speed of a car (in km/h & m/s) that travels 240 miles in 6 hours. Given that 1-mile = km = 1609 m
9 PHYSICS MR BALDWIN Speed & Velocity 9/17/2014 AIM: What is the difference between constant and changing motion?(What is acceleration?)DO NOW: Look at the runner below. What can you infer about the runner?
10 Look at the picture below Look at the picture below. What can you infer about the runner in red shorts?
11 CHECK: Can you write other forms of the equation to determine the other two quantities t & d?
12 QUANTITY & SYMBOL Distance d Time t Velocity; speed v Mass m UNITS meters (m; km; mi)seconds (s)meters/sec (m/s)Km/hmphkilogram (kg)
13 Uniform & Accelerated Motion Uniform motion refers to motion that has a constant velocitySpeed & direction remains the sameSuch as your car on cruise controlMoving at 50 mph on a straight roadAccelerated motion refers to motion with changing velocityAs you round a curbHit the gas or brake
14 Acceleration Acceleration is the change of velocity divided by time. Where a: acceleration; vf: final velocity; vi:initial velocityDetermine its Unit.Unit: m/s2
15 What is the acceleration of a car whose speed increases from 15 m/s (about 34 mi/h) to 25 m/s (about 56 mi/h) in 20s?
16 PHYSICS MR BALDWIN Speed & Velocity 9/18/2014 AIM: What is motion and how does it change?DO NOW: A skater increases his speed from 2.0 m/s to 10.0 m/s in 3.0 s. What is his acceleration?Home Work: Worksheet 2.2
17 Check Which of the following statements correctly define acceleration? Acceleration is the rate of change of displacement of an object.Acceleration is the rate of change of velocity of an object.Acceleration is the amount of distance covered in unit time.Acceleration is the rate of change of speed of an object.
18 Accelerated MotionAcceleration is also a vector. Therefore, we need the sign.Determine the car’s acceleration.What can you infer about the value of the acceleration?Deceleration occurs when the acceleration is opposite in direction to the velocity.
19 CheckWhat happens when the velocity vector and the acceleration vector of an object in motion are in same direction?The acceleration of the object increases.The speed of the object increases.The object comes to rest.The speed of the object decreases.
20 CheckA car is moving with an initial velocity of vi m/s. After reaching a highway, it moves with a constant acceleration of a m/s2, what will be the velocity (vf) of the car after traveling for t seconds?vf = vi + atvf = vi + 2atvf2 = vi2 + 2atvf = vi – atvf = vi + atvf = vi + 2atvf2 = vi2 + 2atvf = vi – at
21 PHYSICS MR BALDWIN Accelerated Motion 9/19/2014 AIM: How are acceleration, velocity, distance and time related?DO NOW: Look at the runner in the red shorts below. What can you infer about the runner’s velocity and distance for each time interval?
22 Changing VelocityAccelerationThere are two major indicators of the change in velocity in this motion diagram. Can you identify them?The change in the spacing of the dots and the differences in the lengths of the velocity vectors indicate the changes in velocity.
23 Can you identify which one is speeding up and which one is slowing down? AccelerationChanging VelocityIf an object speeds up, each subsequent velocity vector is longer. Also, the subsequent distances increases.If the object slows down, … (you fill in the rest)
24 What can be said about the distances here? AccelerationVelocity-Time GraphsWhat can be said about the distances here?
29 Average Speed & Distance Traveled During Constant Acceleration In addition, as the velocity is increasing at a constant rate, we know that
30 Equations of Motion (Please write on Index cards)
31 INITIAL VELOCITY IS ZERO SOME KEY PHRASESOBJECT STARTS FROM RESTOBJECT RELEASED FROM RESTOBJECT DROPPEDOBJECT STOPSOBJECT COMES TO RESTOBJECT SLOWS TO A HALTINITIAL VELOCITY IS ZEROFINAL VELOCITY IS ZERO
40 NOTEThe equations can be used to find time of flight from speed or distance, respectively.Remember that an object thrown into the air represents two mirror-image flights, one up and the other down.Acceleration of an object moving up is negative.Magnitude of the acceleration up or down is the same
41 PHYSICS MR BALDWIN Freefall Motion 9/23/2014 AIM: How is the motion of an object affected when projected upwards?DO NOW: Describe the velocity of an object after it has been thrown vertically upwards with a speed of 20 m/s and returns back to it initial position.Home Work: Worksheet - Acceleration due to gravity
42 Back to “HOW FAR?” Recall that But for the object thrown upwards with some velocity, let d become ‘h’ (to stand for height), and vi is different from 0, with the acceleration a = -g (only due to gravity):DERIVE THE EQUATION FOR HEIGHT
43 Now to “HOW FAST?” Recall that But for the object thrown upwards with some vi different from 0, with the acceleration a= -g (only due to gravity):DERIVE THE EQUATION FOR OBJECT’S VELOCITY.
44 From this, we can answer “HOW LONG” If we know the height to which the object rises, we can determine HOW LONG it takes to get there.What happens to the velocity at the top of the object’s motion?vf = 0DERIVE THE EQUATION FOR THE TIME TAKEN FOR THE OBJECT TO REACH MAXIMUM HEIGHT.
45 “HOW LONG”: What goes up must come down When we throw an object UP and it returns to its initial position, the total displacement is…_________Time of FLIGHT is duration of time object is in the aird = 0DERIVE THE EQUATION FOR THE TIME OF FLIGHT
46 TEST YOURSELF:A ball goes up We have a situation to consider…The ball’s direction of travel is in the OPPOSITE direction of its acceleration.THUS…SO, what will happen to the speed as the ball rises?DECREASELet’s say we gave the ball an initial upward velocity of about 40 m/s.After 2 s, what will the velocity of the ball be?How long will the ball be in the air?How far will it rise in the air?
49 PHYSICS MR BALDWIN Graphing Motion 9/29 & 30/2014 AIM: How do we graphically represent the motion of an object?DO NOW: Draw a distance-time graph of the functionDraw a velocity-time graph of the functionYou can USE your calculator.Home Work: Worksheet - Analyzing Graphs of Motion Without Numbers
50 CHECKLooking at the equation of motion for distance of accelerated motion, what will the resulting distance-time graph look like?PARABOLALooking at the equation of motion for velocity of accelerated motion, what will the resulting velocity-time graph look like?STRAIGHT LINE (LINEAR)
51 Distance-Time graph of Uniformly Accelerated Motion What type of curve is this?
52 Finding Speed: What can you say about the slope of the graph at any time? The slope of the tangent to the distance-time graph at any point is the instantaneous speed at that point.8.00 m/s4.00 m/s
53 Speed-Time Graph of Uniformly Accelerated Motion What information can we gain from the Slope of the velocity-time graph?
54 Speed-Time Graph of Uniformly Accelerated Motion Slope gives acceleration of the body at each point.Slope 2.00 m/s24.00 m/s2.00 s
55 Distance-Time graph of an object moving at Constant Speed This is a graph of d vs. t for an object moving with uniform motion.The speed is the slope of the d-t graph.CHECKWhich line has the greater speed? Explain.
56 Graphical Analysis of Linear Motion On the left we have a graph of velocity-time for an object with varying velocity; on the right we have the resulting distance-time graph.CHECKWhat can you infer about the motions of the object during periods 1 – 4?
57 Graphical Analysis of Linear Motion CHECKHow would you find the area under the velocity-time graph?The distance, d, is the area beneath the velocity-time graph.The smaller the rectangles the more precise the distance
58 PREDICTING MOTION GRAPHS Draw a distance-time graph for an object 10 m away from a starting point at rest for 10 s.Draw a distance-time graph for an object moving at a constant rate of 2.0 m/s.Draw a distance-time graph for an object moving at a constant rate of 4.0 m/s.Draw a velocity-time graph for an object moving at a constant rate of 10 m/s.Draw a velocity-time graph for an object moving at a constant rate of –10 m/s.Draw a velocity-time graph for an object accelerating at a constant rate of 2.0 m/s2.Draw a velocity-time graph for an object decelerating at a constant rate of 2.0 m/s2.