Acceleration March 2, 2010

Objectives 1. Define acceleration and deceleration 2. Describe the relationship between velocity and acceleration 3. Calculate acceleration

Speed vs Velocity? Speed – how fast an object is changing its position Velocity – an object’s speed and direction

Velocities can be combined. Rowing downstream at 16 km/h southeast on a river which is moving 10 km/h southeast results in a total velocity of 26 km/h southeast.

Rockets are launched in the same direction as the earth rotates. Added boost of 1800 km/h!

Acceleration the rate of change in velocity

final velocity – initial velocity time Acceleration

A = V f – V i T Acceleration equation

A =  V T  is pronounced delta

Acceleration units km / h /h or km / h 2 m/s/s m / s 2 km / h /s kilometers per hour per hour meters per second per second kilometers per hour per second

Example problem A roller coaster’s speed at the top of a hill is 10 m/s. Two seconds later, it reaches the bottom of the hill with a speed of 26 m/s. What is the acceleration of the roller coaster? ViVi VfVf t

A =  V T Acceleration equation

A =  V T Final velocity = 26 m/s Initial velocity = 10 m/s Time = 2 s A = 26 m/s – 10 m/s = 16 m/s = 8 m/s/s 2s 2s

Deceleration Negative acceleration

Example Problem At the end of a race, a bicycle is decelerated from a velocity of 12 m/s to a rest position in 30 seconds. What is the deceleration of this bicycle? ViVi VfVf t

Final velocity = 0 m/s Initial velocity = 12 m/s Time = 30 s

A =  V T Acceleration equation

A =  V T Final velocity = 0 m/s Initial velocity = 12 m/s Time = 30 s A = 0 m/s – 12 m/s = -12 m/s = -0.4 m/s/s 30s 30s

If a rocket in space is moving at a constant velocity of 9.8 m/s and then uses its propulsion system to accelerate to 12.0 m/s during a 3.0 minute burn, what would be the acceleration of the rocket? A = V f – V i t

If a rocket in space is moving at a constant velocity of 9.8 m/s and then uses its propulsion system to accelerate to 12.0 m/s during a 3.0 minute burn, what would be the acceleration of the rocket? A = V f – 9.8 m/s t

If a rocket in space is moving at a constant velocity of 9.8 m/s and then uses its propulsion system to accelerate to 12.0 m/s during a 3.0 minute burn, what would be the acceleration of the rocket? A = 12.0 m/s – 9.8 m/s t

If a rocket in space is moving at a constant velocity of 9.8 m/s and then uses its propulsion system to accelerate to 12.0 m/s during a 3.0 minute burn, what would be the acceleration of the rocket? A = 12.0 m/s – 9.8 m/s 3 min A = 0.73 m/s/min