What is motion?

STANDARDS P8B1: The student will use examples to explain the concept of inertia in everyday situations. (4.1) P8B1: The student will describe the following interactions: Speed, Velocity, and acceleration. (4.3)

STANDARDS P8B1: The student will provide evidence to demonstrate the relationship between force and motion. (4.6) The student will identify the force(s) acting on moving and stationary objects. (4.7)

Motion is a change in position, measured by distance and time

A reference point is needed to measure movement

Are you moving right now?

What is your reference point?

Earth rotates on its axis at 1,100 mph Earth orbits the Sun at 68,000 mph

The whole galaxy rotates at 490,000 mph

Frames of Reference

Speed is the distance traveled by a moving object over a period of time

distance Speed = time

distance Speed = time 10 feet = = 2 feet/min 5 minutes A snail crawls 10 feet in 5 minutes. What is the speed of the snail? distance Speed = time 10 feet = = 2 feet/min 5 minutes

Velocity is speed in a given direction

Velocity It has both speed and direction.

Do all these planes have the same speed? Is their velocity different?

Newton's Laws

Newton’s First Law of Motion https://www.youtube.com/watch?v=LEHR8YQNm_Q What is Newton’s first law of motion? What are some examples of unbalanced forces?

First Law of Motion An object at rest will remain at rest, and a moving object will remain at a constant velocity unless acted on by an outside force.

Common Example of First Law People commonly encounter the 1st law while sitting in a fast moving vehicle that comes to a sudden stop

1st Law An outside force (the collision) stop the vehicle, but passengers continue to move long after the vehicle is stopped

1st Law Why were the passengers thrown forward?

            Newton's Laws of Motion Newton’s First Law: A body continues at rest or in motion in a straight line unless acted on by some force.   Q: Why do we not observe this usually? Q: Can you think of other examples (like the astronaut) of times when we do?

Second Law of Motion F = Ma Force = mass X acceleration

             Newton's Laws of Motion Newton’s Second Law:  

What does F = ma say? F = ma basically means that the force of an object comes from its mass and its acceleration. Something very massive (high mass) that’s changing speed very slowly (low acceleration), like a glacier, can still have great force. Something very small (low mass) that’s changing speed very quickly (high acceleration), like a bullet, can still have a great force. Something very small changing speed very slowly will have a very weak force.

2nd Law They both have the same acceleration (gravity) That means the one with more mass will have more force when it hits the ground. Which will have more force, the elephant or the hockey puck?

For every action, there is an equal and opposite reaction. Third Law of Motion For every action, there is an equal and opposite reaction.

3rd Law Forces come in pairs – action and reaction If body A exerts a force on body B, the body B exerts an equal and opposite force on body A

                 Newton's Laws of Motion Newton’s Third Law: To every action, there is an equal and opposite reaction.

Newton’s 3rd Law Example

Another Example The engine pushes gases down. The rocket goes up.