Velocity and Velocity and AccelerationAcceleration

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VelocityVelocity

Speed only describes Speed only describes how fast something is how fast something is movingmoving

Velocity describes both Velocity describes both speed AND direction!speed AND direction!

VelocityVelocity Concep question:Concep question:

Picture two sports cars racing down Picture two sports cars racing down the highway. The Ferrari is traveling the highway. The Ferrari is traveling west while the Lamborghini is west while the Lamborghini is traveling east. They both have a traveling east. They both have a speed of 100km/h. What can you speed of 100km/h. What can you conclude about their velocities?conclude about their velocities?a.a.Ferrari’s v is greater Ferrari’s v is greater b. Lamborghini’s v is greater b. Lamborghini’s v is greater

c. Their velocities are the samec. Their velocities are the same d. Their velocities are differentd. Their velocities are different

VelocityVelocity The answer is d. Both cars The answer is d. Both cars

have the same speed, have the same speed, however the direction in however the direction in which they are traveling is which they are traveling is different. Their velocities different. Their velocities are different because their are different because their directions are different.directions are different.

Change in velocityChange in velocity

Speed may not always Speed may not always be constant.be constant.

The velocity of an object The velocity of an object may change, even if the may change, even if the speed remains the speed remains the same.same.

AccelerationAcceleration

Acceleration is the rate of Acceleration is the rate of change of velocitychange of velocity

Velocity includes both speed Velocity includes both speed and direction, therefore and direction, therefore acceleration is both the rate acceleration is both the rate of change in velocity and of change in velocity and direction of that change.direction of that change.

AccelerationAcceleration

If acceleration is in the same If acceleration is in the same direction as the object, the direction as the object, the objects speeds up.objects speeds up.

If acceleration is the If acceleration is the opposite direction as the opposite direction as the object, the object slows object, the object slows down.down.

AccelerationAcceleration

Acceleration also depends on Acceleration also depends on the time interval.the time interval.

To calculate the acceleration To calculate the acceleration of an object, divide the of an object, divide the change in velocity by the change in velocity by the time.time. a=a=vvff-v-vii or or ΔvΔv t t t t

Acceleration UnitsAcceleration Units

The unit for velocity is meters / The unit for velocity is meters / second m/ssecond m/s

The unit for time is seconds (s)The unit for time is seconds (s) Therefore, the unit for acceleration Therefore, the unit for acceleration

is is meters/seconds meters/seconds = m/s = m/s22

secondsseconds

““Meters per second squared”Meters per second squared”

Acceleration Sample Acceleration Sample ProblemProblem A race car sits at the starting line A race car sits at the starting line

at Atco raceway. The light turns at Atco raceway. The light turns green and the driver presses the green and the driver presses the pedal to the metal. The velocity pedal to the metal. The velocity changes from 0 m/s to 60m/s in 6 changes from 0 m/s to 60m/s in 6 seconds. What is the acceleration seconds. What is the acceleration of the car? of the car?

Solution:Solution:

List the known information:List the known information:

initial velocity (vinitial velocity (vii): 0 m/s): 0 m/s

Final velocity (vFinal velocity (vff): 60 m/s): 60 m/s

Time: 6 secondsTime: 6 seconds

A= A= 60m/s – 0 m/s60m/s – 0 m/s = 10 m/s = 10 m/s22

6 s6 s

Homework:Homework:

Questions 1-3 on page Questions 1-3 on page 67.67.

Complete mini-lab…Complete mini-lab…

Does greater velocity Does greater velocity require greater require greater acceleration?acceleration?