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A push or pull on an object.
Described by:
A force gives an object energy to:
Force
•STRENGTH•DIRECTION
•STOP MOVING•START MOVING•CHANGE DIRECTION
Contact and Noncontact Sports
How do these relate to the title of this lesson? (Gravity and Friction?)
Contact = frictionNoncontact = gravity
Contact Noncontact
A push or pull on one object by another that is touching it.
Contact Force
Contact forces can be: Strong OR Weak
A force that one object can apply to another object without touching it.
Noncontact Force
Examples Include:
Gravity Magnetic Force Electric Force
can be used to show forces.
The of an arrow shows the
of the force.
The that the arrow points shows the direction in which the
The stronger the force the the arrow.
Strength and Direction of Forces
ARROWS
DIRECTION
LENGTHSTRENGTH
FORCE WAS APPLIED
LONGER
The SI unit for force is the
The symbol for Newton is
One Newton = about the force you exert to lift a lime.
Named after:
Strength and Direction of Forces
NEWTON
N
Sir Isaac Newton (founder of physics)
An attractive force that exists between all objects that have mass.
Gravity
Force of gravity On EARTH the force of gravity = 9.8 m/s2
All objects fall to the Earth at an acceleration of 9.8m/s2 due to the force of gravity.
Sir Isaac Newton (1600’s)
The law states:
Factors Affecting Gravity
The Law of Universal Gravitation
•MASS•DISTANCE
All objects are attracted to each other by a gravitational force. The strength of force depends on the MASS of each object and the DISTANCE between them.
When the mass of one or both objects the gravitational force between them also
Regardless of the amount of mass an object has the will be the
Each object exerts the attraction on the other object.
Gravitational Force and MASS
INCREASES
INCREASES
FORCE ARROWS
SAME SIZE
SAME
The attraction between objects as the between the object
Gravitational force and DISTANCE
DECREASES
DISTANCE INCREASES
The gravitational force exerted on an object.
Weight is measured in
Near Earth’s surface the object’s weight is the
Weight
NEWTONS
FORCE DUE TO GRAVITY
Weight and mass are related, but ARE NOT the same.
Weight can due to
Mass change
FORCE =
Weight and Mass on Earth
CHANGE GRAVITY
DOES NOT
MASS x ACCELERATION
F =
Weight on Earth =
M x A
MASS x 9.8m/s2 (acceleration due to the force of gravity)
What would an object with a mass of 10 kg weigh?
If your mass was 50kg, what would your weight be?
Examples:
The combination of all the forces acting on an object.
To calculate the net force:
◦ If the forces act in the same direction they are added together.
◦ If forces act in opposite directions they are subtracted.
Net Force
Forces acting on an object that combine and form a net force that is not zero.
Unbalanced forces cause an object to move. Forces moving in the same direction are
Forces moving in the opposite direction are
Combining Forces - Unbalanced
ADDED
SUBTRACTED
Forces acting on an object that combine and form a net force of ZERO. NO change in motion.
Combining Forces – Balanced Forces
A force that resists the motion of two surfaces that are touching.
Types of friction
Friction
•STATIC FRICTION
•SLIDING FRICTION
•FLUID FRICTION
A force produced by a fluid (gases or liquids) Examples: engine oil, grease
Air resistance
Air resistance is affected by:
*objects with more surface area have more air resistance**
Fluid Friction
•SHAPE•SIZE•MASS
•a type of fluid friction•Upward force exerted on falling objects.
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