Calculators everyday this week! Agenda 4/6/10 Collect Bouncing Ball Lab. Acceleration and Deceleration (page #10). Start homework. Homework: Acceleration Calculations WS (page #11). Motion Quiz on Friday (see motion study guide and topics sheet) Calculators everyday this week!

Acceleration and Deceleration ACCELERATION measures the change in the velocity of an object. For example, a car may be accelerating at 5 km/hr for every second. This means that every second the car is going 5 km/hr faster. Therefore, the first second the car is traveling 5 km/hr; The second, second________________________. The third second __________________________. To solve for acceleration or deceleration, you must know the objects initial velocity (Vi) and final velocity (Vf) of the moving object and the time between these two velocities. 10 km/hr 15 km/hr

New Formula Acceleration/Deceleration (a): a = Vf - Vi t Vf = Final Velocity Vi = Initial (starting) Velocity t = time

Sample Problem #1 If a stopped car obtains a velocity of 60 km/hr in 10 seconds, what is its acceleration? a = Vf - Vi t a = 60 km/hr - 0 km/hr 10 seconds a = 60 km/hr 10 sec a = 6.0 km/hr sec

Sample Problem #2 What is the acceleration of a grasshopper that jumps from standing still to a final velocity of 50 m/s in a time of 0.25 seconds? a = Vf - Vi t a = 50 m/s - 0 m/s 0.25 seconds a = 50 m/s 0.25 sec a = 200.0 m/s or m/s2 sec

Sample Problem #3 What is the acceleration of Lindsey who ran the 100 m dash if she reached a speed of 19 m/s in 9.5 seconds? a = Vf - Vi t a = 19 m/s - 0 m/s 9.5 seconds a = 19 m/s 9.5 sec a = 2.0 m/s or m/s2 sec

What is deceleration? DECELERATION is simply negative acceleration. It measures the change in velocity of a moving object that is slowing down. When brakes are applied to a car, it is decelerating.

Graphing Motion All motion continues in a straight line unless an outside force is exerted upon it. All motion can be expressed as a graphing relationship between distance and time. A graph for constant speed is always a straight line such as the one at the right measuring the speed of two cars. Which car is moving faster? Explain. Car A Car A has traveled a greater distance in a shorter period of time.

Graphing Motion Examine the graph. Explain what happened at section B of the graph. Car had stopped!

Graphing Motion Use the data table and graph grid to the right. Graph the speed of the car that traveled 500 km in 5 hours. Make sure to correctly label the x-axis and y-axis. Data Table Time (hrs) Distance (km) 1 100 2 200 3 4 400 5 500 What was the car doing between the second and third hour? Stopped. Did the car go a constant speed during the journey? No. Car stopped for a portion of time.

Graphing Motion What is the shape of the line on the graph for acceleration? What is the shape of the line on the graph for deceleration? DOWNWARD UPWARD

Graphing Motion Using the deceleration graph, what happens to the distance traveled per unit of time? Distance decreases as time increases. Object is slowing down (decelerating).

Speed vs. Time Graphs ACCELERATION Remember we know have two (2) acceleration graphs:

Speed vs. Time Graph DECELERATION Remember we know have two (2) deceleration graphs:

Speed vs. Graph CONSTANT SPEED Remember we know have two (2) constant speed graphs: