-motion is the state in which one object’s distance from another is changing
TRANSCRIPT
-Motion is the state in which one object’s distancefrom another is changing.
-Motion is the state in which one object’s distancefrom another is changing.
How do you know that something is moving?
• A reference point is needed to determine if an object is in motion.
• A reference point is a place or object used to determine if an object is in motion
• An object is in motion if it changes position relative to the 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
Speed = distancetime
A snail crawls 10 feet in 5 minutes.What is the speed of the snail?
Constant Speed
• When an object is traveling at the same speed while it is in motion
• Example: using the cruise control on a car
It has bothspeed and direction.
Do all these planes have the same speed?
Istheirvelocitydifferent?
What is acceleration?• Rate at which
velocity changes
• In science, it means speed up, slow down, or change direction
Calculating acceleration
• Acceleration= Final velocity-Initial velocity
time
A = VF-VI
t
• A car starts from rest and accelerates over a time of 5.21 seconds for a distance of 110 m. Determine the acceleration of the car.
Newton’s First Law of Motion-
An object at rest or in motion will remain that way until acted upon by an outside unbalanced 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:
Q: Why do we not observe this usually?
Force = mass X acceleration
Newton’s 2nd Law
F = Ma
Newton's Laws of Motion
Newton’s Second Law:
F ma
What does F = ma say?F = ma means that the force of an object comes from its mass and its acceleration.
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.
Something very massive (high mass) that’s changing speed very slowly (low acceleration), like a glacier, can still have great 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?
Newton’s 3rd Law -For every action,there is an equaland oppositereaction.
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.
Example
• The engine pushesgases down.
• The rocket goes up.