10.2 Acceleration
I CAN:
-IDENTIFY THAT ACCELERATION IS A VECTOR PROPERTY.
-CALCULATE AVERAGE ACCELERATION OF AN OBJECT.
-DETERMINE IF ACCELERATION IS POSITIVE OR NEGATIVE.
-DISTINGUISH BETWEEN CONSTANT AND ZERO ACCELERATION.
-RECOGNIZE CONSTANT ACCELERATION.
Acceleration

Acceleration: the rate at which velocity changes over time.

An object accelerates if its SPEED, DIRECTION, OR BOTH change.

What about slowing down?

Typically what you think of as acceleration also increases velocity.
Example of changing speed

You are facing south on your bike and start moving. You speed up
as you go. Every second, your southward velocity increases. After
1s, your velocity is 1m/s south. After 2s, your velocity is 2m/s south
and so on… Your acceleration can be expressed as an increase of
one meter per second per second (1m/s/s or 1m/s2)
Example of changing direction

Skaters on the ice, each lap in Nascar, the moon around Earth,
riding a Ferris wheel!

Acceleration is defined as the rate in which velocity changes.

Velocity includes both speed AND direction.

You can actually accelerate without ever speeding up or slowing
down.

What about standing still on Earth?
Circular Motion

An object traveling in a circular motion is always changing
direction.

Acceleration that occurs in uniform circular motion is known as
Centripetal Acceleration.
Calculating Acceleration

Acceleration= final velocity-initial velocity/change in time

Can be positive or negative

Ex: You are rollerblading and see a large rock in your path, so you slow
down and swerve. Friend says, “Wow that was great acceleration.”

Is he correct?
Practice acceleration

I am accelerating to a stop. I was
originally going at 20m/s and
stopped in 0.50 s.

Solve…

Answer: -40 m/s/s or -40 m/s2
Velocity-time graph

Previously learned that an objects
speed can be determine from a
distance/time graph.

Acceleration can be determined
from a velocity/time graph.

What does the straight line
represent?

Which would be positive
acceleration?

Which would be negative
acceleration?
Homework Practice Problems
(pg.328)

Natalie accelerates her skateboard along a straight path from 0 m/s
to 4.0 m/s in 2.5 s. Find her average acceleration.

A turtle swimming in a straight line toward the shore has a speed of
0.50 m/s. After 4.0 s, its speed is 0.80 m/s. What is the turtles average
acceleration?

Find the average acceleration of a northbound subway train that
slows down from 12 m/s to 9.6 m/s in 0.8 s.

Marisa’s car accelerates at an average rate of 2.6 m/s2. Calculate
how long it takes her car to speed up from 24.6 m/s to 26.8 m/s.

A cyclist travels at a constant velocity of 4.5 m/s westward, and
then speeds up with a steady acceleration of 2.3 m/s2. Calculate
the cyclist’s speed after accelerating for 5.0 s.