Acceleration 2.2

Objectives Perform acceleration calculations. Explain how positive and negative acceleration affect motion. CLE 3202.3.1 Investigate the relationships among speed, position, time, velocity, and acceleration.

Acceleration * change in speed or direction A. Acceleration - rate of change in velocity * change in speed or direction

Acceleration 1. Positive acceleration - speed is increasing. “speeding up” 2. Negative acceleration - speed is decreasing. “slowing down”

Negative Acceleration (Deceleration) Decreasing or (-) velocity Slowing down

Acceleration 3. When an object changes speed or direction, it is accelerating.

Acceleration 2 Changing Direction The speed of the carousel is constant. Why is acceleration changing?

Acceleration, Speed and Velocity 2 Acceleration, Speed and Velocity The speed of the horses in this carousel is constant, but the horses are accelerating because their direction is changing constantly. ** Acceleration occurs when an object changes its speed, its direction, or both.

Roller coasters B. Amusement park acceleration - roller coasters - remember 1. Changes in speed cause acceleration. 2. Changes in direction cause acceleration

Acceleration Rate at which the velocity of a moving object changes Final Velocity – Starting Velocity Time Change in Velocity ÷ Time

t a C. Acceleration Acceleration the rate of change of velocity vf - vi t C. Acceleration Acceleration the rate of change of velocity change in speed or direction a: acceleration vf: final velocity vi: initial (starting) velocity t: time

Equation a = ( vf - vi ) ÷ t v = ( vf - vi ) = change in = delta -

Calculating Acceleration C. Calculating acceleration 1. Acceleration = change in velocity / time 2. Change in velocity = final velocity - initial velocity 3. Unit for acceleration - meters per second squared (m/s2)

To find change in velocity, subtract the starting velocity (vi ) from the final velocity (vf) acceleration = change in velocity time a = vf - vi / time

Calculating Acceleration 2 Calculating Acceleration Using this expression for the change in velocity, the acceleration can be calculated from the following equation:

t a D. Calculations a = (vf - vi) ÷ t t = 3 s A roller coaster starts down a hill at 10 m/s. Three seconds later, its speed is 32 m/s. What is the roller coaster’s acceleration? GIVEN: vi = 10 m/s t = 3 s vf = 32 m/s a = ? WORK: a = (vf - vi) ÷ t a = (32m/s - 10m/s) ÷ (3s) a = 22 m/s ÷ 3 s a = 7.3 m/s2 a vf - vi t

http://www. biologycorner http://www.biologycorner.com/physics/mechanics/problemset_velocity_acceleration.html

Graphing Acceleration The slope of a line on a graph showing speed and time. Changes in slope show change in acceleration. Page 49-50

E. Graphing Motion slope = +ve = speeds up -ve = slows down Speed-Time Graph acceleration +ve = speeds up -ve = slows down slope = straight line = flat line = constant accel. no accel. (constant velocity)

E. Graphing Motion Speed-Time Graph Specify the time period when the object was... slowing down 5 to 10 seconds speeding up 0 to 3 seconds moving at a constant speed 3 to 5 seconds not moving 0 & 10 seconds

CLE 3202.3.1 Investigate the relationships among speed, position, time, velocity, and acceleration. Objective: Perform calculations involving time, distance, velocity, and acceleration.

http://phet.colorado.edu/en/simulation/moving-man

Acceleration is the rate of change of __________. Section Check 2 Question 1 Acceleration is the rate of change of __________.

Section Check 2 Answer The correct answer is velocity. Acceleration occurs when an object changes its speed, direction, or both.

Which is NOT a form of acceleration? Section Check 2 Question 2 Which is NOT a form of acceleration? A. maintaining a constant speed and direction B. speeding up C. slowing down D. turning

Section Check 2 Answer The answer is A. Any change of speed or direction results in acceleration.

Section Check 2 Question 3 What is the acceleration of a hockey player who is skating at 10 m/s and comes to a complete stop in 2 s? A. 5 m/s2 B. -5 m/s2 C. 20 m/s2 D. -20 m/s2

Objective: Explain how positive and negative acceleration affect motion. Section Check 2 Answer The answer is B. Calculate acceleration by subtracting initial velocity (10 m/s) from final velocity (0), then dividing by the time interval (2s). (0 m/s – 10 m/s) = – 5 m/s2 2s

http://glencoe. mcgraw-hill http://glencoe.mcgraw-hill.com/sites/dl/free/0078600510/161752/00035808.html

CLE 3202.3.1 Investigate the relationships among speed, position, time, velocity, and acceleration. Objective: Perform calculations involving time, distance, velocity, and acceleration. Objective: Explain how positive and negative acceleration affect motion.

Objectives Perform calculations involving time, distance, velocity, and acceleration. Explain how positive and negative acceleration affect motion. CLE 3202.3.1 Investigate the relationships among speed, position, time, velocity, and acceleration.