22 and 23: Acceleration, Motion, and Forces

1
2-2 and 2-3 Acceleration, Motion, and Forces

• 24 points

2
2-2 Rough Outline

• Acceleration
• Speeding up and slowing down
• Changing direction
• Calculating Acceleration
• Calculating acceleration
• Calculating - acceleration
• Amusement park acceleration

3
2-3 Rough Outline

• What is force?
• Changing motion
• Balanced forces
• Unbalanced forces
• Inertia and mass
• Newtons Law of Motion
• Newtons First Law of motion
• III. What happens in a crash/Safety Belts

4
Acceleration, speed, and velocity

• The rate of change of position is called
• Speed or velocity
• The rate of change of velocity is called
• acceleration
• Give an example of an object that possesses a
  positive acceleration
• Car speeding up
• Give an example of an object with a negative
  acceleration
• Car slowing down.

5
What is the distance?

• Explain an example where the acceleration is 0,
  but the velocity is NOT 0
• When an object is coasting. For example, the
  probes they send to Mars coast for a good bit of
  the trip.
• Object accelerate not only when they speed up or
  slow down, but also when they _____ _____.
• Change direction
• Give the formula for acceleration
• A (vf vi)/t

6
Example

• A car is traveling 28 m/s when it slows for a
  sudden yellow light. It takes 6 seconds for the
  car to come to a stop. What is the acceleration?
• Step One
• A (vf vi)/t
• Step Two
• A (0 28)/6
• Step Three
• A -4.7 m/s2

7
Your turn Please do 6 and 7 on page 51.
8
What is force?

• A force is a _____ or a _____.
• Push, pull
• When a force affects and object, it always causes
  the object to _______.
• Accelerate
• If you jump into the air, you actually MOVE THE
  EARTH, when you hit the ground again, because you
  have exerted a force on the Earth. Why cant you
  see or feel the Earths movement?
• Because the Earth is really really big and we
  really really arent. While the Earth does move,
  it doesnt move much at all.

9
Forces, continued

• Sometimes, forces do NOT cause an acceleration.
  What do we call these types of forces?
• Balanced
• When forces are unbalanced, though, there IS an
  acceleration in the direction of the ____ ____.
• Net force.

10
What is the Net Force?
8 N East
2 N West
6 N East
11
What is the Net Force?
4 N East
5 N West
1 N West
12
What is the Net Force?
3 N East
3 N West
No net force (balanced)
13
Inertia and Mass

• Inertia is the ability of an object to resist any
  change in its _____.
• Motion
• Objects in Motion tend to
• Stay in motion
• Objects at rest tend to
• Stay at rest
• As an objects ____ increases, so does its
  inertia
• Mass
• Give an example of how inertia affects your life.

14
Car crashes

• You have inertia, and if your car stops suddenly,
  your body will tend to continue
• Moving
• That is bad. Why is it bad that your body tends
  to continue moving?
• Windshield. Dashboard. Other ouchies.
• What are two safety devices that stop your bodys
  motion more safely than the windshield or the
  dashboard.
• Safety belt
• Airbag.
• You are important and I like that youre here.
  Please use your safety belt!