motion and force are governed by three laws called newton’s laws of motion
TRANSCRIPT
Forces and Motion
Motion and Force are governed by three laws
Called Newton’s Laws of Motion
Sir Isaac NewtonThe unit “force”, is named after himResearched gravity in the 1600’s He believed that every object in the universe
was pulling on every objectThis theory is called Newton’s Law of
Universal Gravitation.- Newton said in this theory that gravity depends on the mass of the object and the distance between them.
ForceBuoyancyThrustLiftDrag
Air resistance
Friction
Gravity
Balanced force
Unbalanced force
Science is a new language – the words explain what is happening. Some of the words are:
Force- any push or pull from one object to another.
- Units of force are Newton (N) and pound (lb)
- touch- push or pull on a door- magnetic force- compass needle
pulled north- buoyancy force- lifts lighter
substances out of denser substances
Newton’s 1st lawAn object at rest tends to stay at rest,
and an object in constant motion tends to stay in motion, unless acted upon by an unbalanced force. (also known as “law of inertia”
Balanced force- when forces act on an object without changing its motion.
Unbalanced force- force that causes an object to change its motion.
Demo 1
An Airplane has special names for its forces- thrust- the engines pull or push-lift- air moves around the wings then the plane rises-drag- broad, flat surfaces of the plane hit the air and pulls back on the rest of the plane. This process slows the plane down.- gravity- pulling the plane down to the ground.
What causes a dropped object to fall to the ground?- Gravity
Some gravity exists between you and the person next to you, why are you pulled toward Earth and not toward the other person? (talk in your group)- Gravity depends on mass and Earth has greater mass than a person
What is friction?- Force that keeps the surface of an object from easily moving past
the surface of another object
What things influence the amount of friction between objects?
- how rough or smooth a surface is, how hard objects are pressed together and the mass of the object
Friction Rub your hands together quicklyWhat happened?Test the friction of pushing in a chair with and without
weight Imagine the world without friction?
-without friction you would not be able to walk or move around because you would slip on everything- ex: ice on sidewalk or roads
Smooth objects have less friction than rough objects.Friction increases when surfaces are pressed together with
greater force.Friction increases with weight of an object
Imagine you are sky divingWhat slows you down? -Air Also known as air resistance
Drag forces are a result of air resistance Drag slows down objects much like friction.Without air resistance, a feather and a pencil
would fall at the same time.
Newton’s 3rd LawAll forces occur in pairs, and these two forces
are equal in strength and opposite in direction.
Better known as:For every action there is an equal and
opposite re-action
Demo 2
Newton’s 2rd LawThe unbalanced force on an object is equal to
the mass of the object multiplied by its acceleration.
FORCE= Mass x Acceleration How much force must be used to accelerate a 5kg
mass to 2 (m/s)s
5 kg x 2 (m/s)s= 10 N A bicycle rider is moving forward with a force of
200N and there is a 100N pulling back, What is the total force of the bicycle and rider?
200N – 100N= 100N*Acceleration decreases as your mass increases.
Experiment