Laws of Force Mr. Dunnum Physical Science

What is force?  Force is simply a push or pullpush or pull  All forces have both size and direction  Forces are everywhere  Anytime you see something moving, you can be sure that its motion created by a force

How do we measure force?  Scientist express force by using a unit called Newton's  The more the Newton's the greater the force

Net force?  What is net force?  Net force is the result of combining all the forces exerted on an object  Same direction you add them  Opposite directions you subtract them

Unbalanced and Balanced Forces  Unbalanced forces  When the net forces of an object is not zero then it is an unbalanced force.  Unbalanced forces cause nonmoving objects to start moving Balanced forces When the net forces equal zero then the forces are balanced Balanced forces don’t cause objects to move

Newton's first law  If an object is at rest it will remain at rest unless it is affected by an outside force, if an object is moving it will remain moving until it is stopped by an outside force.

Friction  Force that opposes motion between two surfaces  Friction occurs because the surface of any object is rough  A rougher surface creates more friction  The more force the more friction

Sliding/ Rolling Friction  Sliding Friction  Takes more effort and force to move objects by sliding  Ex. Moving furniture Rolling Friction Is important to all means of transportation The friction is smaller and easier to move than sliding

Fluid/Static Friction  Fluid Friction  Also less than sliding friction  Swimmers have to overcome this when swimming Static Friction Prevents an object from moving when force is applied Ex. Moving a refrigerator

Helpful/Harmful Friction  Helpful  Car- friction helps push the car down the road.  It also helps us stop the car with the brakes  Harmful  Car- Cause wear and tear on the motor of the car.

Newton's Second Law  An object acted upon by a force will accelerate in the direction of the force  Acceleration= net force mass F=MA

What is Gravity?  Gravity is the force of attraction between two objects  All matter is affected by gravity  Gravity pulls you down, air resistance pushes you up

Gravity Con.  Small masses have a small gravitational force  The larger masses have a larger gravitational force  If the distance between the two objects is in creased then the gravitational force is reduced

Weight and Mass  Weight  Weight is the gravitational force exerted on an object  Weight changes when the gravitational force changes  Weight is measured on a spring scale Mass The amount of matter in an object, and its value does not change If moved to Jupiter the weight would change, but not the mass Measured by a balance

Newton's Third Law  For every action there is an equal, but opposite reaction  Example when you push a wall it pushes back with the same force

Examples of Newton’s 3 rd Law  Bumper cars  Getting oil changed  Diving in a pool  Dunking a basketball

Free fall and Weightlessness  Free Fall  An object is in free fall when the only force acting on it is gravity Weightlessness Is the condition that occurs in free fall when the weight of an object seems to be zero