Drop everything and read!

Homeroom

Use the textbook to define and add the following words to your glossary:

Acceleration

Velocity-Time Graph

Newton’s Second Law

Warm-up

YouTube - Sid the Science Kid "Ignatz's Inertia"

Inertia Review: Newton’s First Law

•The rate at which velocity changes with time is called acceleration

•Acceleration is a measure of how quickly velocity is changing.

•If velocity does not change, there is no acceleration.

Acceleration

We often refer to acceleration as speeding up BUT it really means any change in velocity.

Ex. A driver slowing down to stop at a light is accelerating.

What does acceleration mean?

•Like velocity, acceleration is also a vector, which means it has both size and direction.

•The direction of acceleration determines whether an object will slow down, speed up, or turn.

Acceleration is a Vector

•We can have:

•Acceleration in the same direction as motion=speed increases

•Acceleration in the opposite direction of motion=speed decreases (negative acceleration)

•Acceleration at a right angle to motion=direction of motion changes

To calculate acceleration, you need to know the starting velocity, the ending velocity, and the time interval which the object changed.

Acceleration= (final velocity-initial velocity)

time

The standard unit for acceleration is meters per second per second which is written as m/s2

(meters per second squared)

Calculating Acceleration

Ama starts sliding with a velocity of 1 m/s. After 3s, her velocity is 7 m/s. What is Ama’s acceleration?

What do you know? Initial velocity=1m/s, final velocity=7m/s, time=3s

Write the formula: a= v(final)-(V)initial

t

Substitute into the formula: a=7m/s-1m/s

3s

Calculate: 6m/s = 2m/s2

3s

Let’s Practice

A man walking at 0.5 m/s accelerates to a velocity of 0.6m/s in 1s. What is his acceleration?

You try!

A train traveling at 10m/s slows down to a complete stop in 20s. What is the acceleration of the train?

You try!

Acceleration, like position and velocity, can change with time.

On a velocity-time graph:

1)A rising line on the velocity-time graph shows positive acceleration (speeding up)

2)A flat line shows no acceleration

3)A falling line shows negative acceleration (slowing down)

Velocity-Time Graphs

Newton’s Second Law of Motion

The acceleration of an object increases with increased force and decreases with increased mass.

IN SIMPLE TERMS: The harder you push, the further it goes. The more mass the object has, the harder it is to move it!