Linear Motion-Acceleration

Acceleration

What happens if you coast down a long hill

without pedaling?

Acceleration

At the top of the hill you move…

Acceleration

slowly

Acceleration

As you go down the hill, your speed…

Acceleration

Gets faster and faster!

You…

Acceleration

Accelerate!

Acceleration

Acceleration is the rate of change in the speed of an object.

Rate of change means the ratio of the amount of change divided by how

much time the change takes.

Acceleration

Acceleration

“The Mazda Miata can go from 0 to 60 in 10

seconds!”

What does that mean?

Acceleration

The car’s speed starts at 0 and reaches 60 mph in 10 seconds.

What is the car’s acceleration?

Acceleration

a = ?

Vf= 60m/hr

Vi= 0 m/hr

t = 10 sec

Acceleration

This means that the car’s speed is

increasing 6 mph each second!

Acceleration

If you were driving and a dog ran in front of your car what would

you do?

Acceleration

If you slammed on your brakes and came to a stop to avoid hitting the

dog, did you accelerate?

Acceleration

Yes, yes you did.

Acceleration

In physics, accelerate refers to any change in speed, (+) or (-), though the word decelerate is used sometimes to describe motion that is slowing down

AccelerationAcceleration is:

•speeding up (accelerating)•slowing down (negative acceleration or decelerating)•turning (changing direction)

The acceleration of an object can be in the same direction as its velocity or in the opposite direction.

Velocity increases when acceleration is in the same direction.

AccelerationUnits for Acceleration

•Most often m/s2

•Ex: 10 m/s2

this means the speed is increasing by 10 m/s every second

Acceleration

What are some examples of Acceleration?

Acceleration

Is it possible to be moving and have

zero acceleration?

Yes!

An object has zero acceleration if it is traveling at constant speed in one direction.

Ex: cruise control in a car

An object moving with constant acceleration has a velocity that changes by the same amount every second

Constant acceleration is sometimes called uniform acceleration in physics problems.

An object can have acceleration but no speed.

A plane starts at rest and ends up going 200 m/s in 10 secs. Calculate acceleration.

A race car starts at 400 m/s and then stops in 20 seconds. Calculate the car’s acceleration.