Acceleration March 2, 2010. Objectives 1. Define acceleration and deceleration 2. Describe the relationship between velocity and acceleration 3. Calculate.

Acceleration

March 2, 2010

Objectives1. 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 = Vf – Vi

T

Acceleration equation

A = V T

is

pronounced delta

Acceleration unitskm / h /h or km / h2

m/s/s m / s2

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?

Vi

Vf

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?

Vi

Vf 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 = Vf – Vi

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 = Vf – 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