Acceleration Movie Galileo First 1 min 15 sec /view/assetGuid/683BF288-CEF9-442D- 9BD5-2AE2BFC7608C /view/assetGuid/683BF288-CEF9-442D- 9BD5-2AE2BFC7608C

Galileo 1600’s 1600’s Studied how things fell Studied how things fell Didn’t have a good clock Didn’t have a good clock Rolled balls down an inclined plane Rolled balls down an inclined plane Found that the speed increased as it rolled down the ramp Found that the speed increased as it rolled down the ramp

Galileo t = 0 t = 1 second t = 2 seconds t = 3 seconds

Acceleration Acceleration is the rate at which velocity (speed or direction) changes. Acceleration is the rate at which velocity (speed or direction) changes. Rate = time Rate = time So, So, acceleration is change in velocity per time. acceleration is change in velocity per time.

3 Types of acceleration 1.Increasing Speed 2.Decreasing speed 3.Changing Direction Because of velocity

A= change in velocity A= change in velocity time time Change in velocity = final – starting velocity velocity A= FV - IV A= FV - IV time time Calculating Acceleration

Acceleration = Velocity (final) - Velocity (original) time A car traveling at 60 mph accelerates to 90 mph in 3 seconds. What is the car’s acceleration?

Acceleration = Velocity (final) - Velocity (original) time A car traveling at 60 mph accelerates to 90 mph in 3 seconds. What is the car’s acceleration? = 90 mph - 60 mph 3 seconds = 30 mph 3 seconds = 10 mph/second

Acceleration = Velocity (final) - Velocity (original) time A car traveling at 60 mph accelerates to 90 mph in 3 seconds. What is the car’s acceleration?

Acceleration = Velocity (final) - Velocity (original) time A car traveling at 60 mph slams on the breaks to avoid hitting a deer. The car comes to a safe stop 6 seconds after applying the breaks. What is the car’s acceleration? = 0 mph - 60 mph 6 seconds = - 60 mph 6 seconds = - 10 miles per hour per second

A car at rest can go 90 km/h in 9 seconds. What is the acceleration?

A person was running down a ramp. They started going 4 m/s down and then ended up going 22 m/s at the bottom. What was the persons acceleration down the ramp.

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Positive acceleration Negative acceleration

- A constant acceleration produces a straight line or linear slope (rise/run). - The slope of a non- linear velocity-time graph (rise/run) will predict an objects instantaneous acceleration. a = v/t - A constant acceleration produces a straight line or linear slope (rise/run). - The slope of a non- linear velocity-time graph (rise/run) will predict an objects instantaneous acceleration. a = v/t

Galileo u Back to Galileo u When things fall they get faster and faster.

Free fall The constant acceleration of an object moving only under the force of gravity is "g". The constant acceleration of an object moving only under the force of gravity is "g". The acceleration caused by gravity is 10 m/s 2 The acceleration caused by gravity is 10 m/s 2 If there was no air, all objects would fall at the same speed If there was no air, all objects would fall at the same speed Doesn’t depend on mass Doesn’t depend on mass After 1 second falling at 10 m/s After 1 second falling at 10 m/s After 2 seconds 20 m/s After 2 seconds 20 m/s 3 seconds 30 m/s 3 seconds 30 m/s

Falling Air resistance will increase as it falls faster Air resistance will increase as it falls faster An upward force on the object An upward force on the object Eventually gravity will balance with air resistance Eventually gravity will balance with air resistance Reaches terminal velocity - highest speed reached by a falling object. Reaches terminal velocity - highest speed reached by a falling object.

Terminal velocity Force of gravity is constant Force of gravity is constant u air resistance increases as you speed up u until the force is equal u Equal forces, no acceleration u constant velocity terminal velocity