This document discusses acceleration, force, and motion. It defines acceleration as the rate of change of velocity and describes how acceleration can be calculated using change in velocity, time, and the acceleration equation. Two types of forces are explained: balanced forces which cause no movement and unbalanced forces which cause movement in the direction of the larger force. Inertia is defined as an object's resistance to changes in motion. Newton's First Law of Motion, also known as the Law of Inertia, states that an object at rest stays at rest and an object in motion stays in motion unless an unbalanced force acts upon it. Examples of inertia and Newton's First Law include car crashes and the use of seat belts. Homework assignments

1. Acceleration and Force
Sec 2 and 3
Thursday 10/3/13

2. Acceleration
• The rate of change of velocity
• Speeding up
– Increasing speed/velocity = positive acceleration
• Slowing down
– Decreasing speed/velocity = negative acceleration

3. 2 ways to Change Velocity
1. moving by going faster
2. Moving by changing direction
Change in velocity = Final velocity – initial velocity

4. Calculating Acceleration
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Acceleration = a
Velocity final = VF
Velocity initial = Vi
Time = t
units = meter per second
squared (m/s2)
Change in Velocity
(Vf – Vi)
Acceleration Time
• Acceleration of gravity = 9.8 m/s2

5. Roller Coasters and acceleration

6. Practice Problems
• A ball is dropped from a cliff and has an
acceleration of 9.8 m/s2 . How long will it take
for the ball to reach a speed of 24.5 m/s?
• A sprinter leaves the starting blocks with an
acceleration of 4.5 m/s2. What is the
sprinter’s speed 2 seconds later?

7. Homework
• 10.3 – Ch 2 Reinforcement section 2

8. Friday 10.4.13
• Drop box Reinforcement sec 2
• Pick up 10.4 – Reinforcement sec 3
• Force Notes

9. Goals
• Explain how force and motion are related
• Describe Inertia
• Explain what forces are present in a car crash

10. Tug-of-War
• The photo shows one team pulling but not
very much moving. In which direction must
the other team be pulling? Why?
• If one team tugs the other over the line, what
can you assume about the pulls exerted by the
two teams?

11. Force
• Is a push or a pull
• What happens to an object when you push or
pull it?
– Transfer of energy from one object to another object

12. 2 types of forces
• Balanced forces – two or more forces acting
on an object in opposite directions causes a
net force of zero (no movement)
• Unbalanced forces – two forces acting on an
object in the same direction (movement in the
direction of the bigger force)

13. Inertia
• The tendency of an object to resist any change
in motion
– An object in motion will stay in motion until
something stops it
– An object at rest will stay at rest until acted on
• The more mass an object has the more inertia
or the harder it is to stop once in motion
– Think of stopping a toy car with your hand and a
real car with your hand. Which one is possible?

14. Newton’s First Law of Motion
• An object in motion stays in motion and an
object at rest stays at rest until an unbalanced
force acts on it.
• Also known as the Law of Inertia
• Ex: car crashes and seat belts

15. Homework
• 10.4 Reinforcement section 3