Transcript Fluid friction

Forces
Force
is a push or a pull.
 a force is described by its strength and by
the direction in which it acts.
 The strength of a force is measured in the
SI unit called the newton (N).

Balanced forces
Balanced Forces-Equal forces acting on
one object in opposite directions .
 Balanced forces acting on an object do not
change the object’s motion .
 When equal forces are exerted in opposite
directions, the net force is zero. forces
cancel out.
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Unbalanced Forces
Forces that produce a nonzero net force,
which changes an object’s motion.
 can cause an object to start moving, stop
moving, or change direction.
 Unbalanced forces acting on an object
result in a net force and cause a change in
the object’s motion.
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Net Force
When the two people push the box in opposite
directions, the net force on the box is the
difference between their individual forces.
 The overall force on an object when all the
individual forces acting on it are added together
 The net force determines whether an object
moves and also in which direction it moves.
Net Force Example
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Friction
The force that one surface exerts on another
when the two surfaces rub against each other.
 In general, smooth surfaces produce less friction
than rough surfaces. The strength of the force of
friction depends on two factors: how hard the
surfaces push together and the types of surfaces
involved.
Friction
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Types of Friction
Sliding friction- Friction that occurs
when one solid surface slides over
another.
 Rolling friction- Friction that occurs
when an object rolls over a surface.
 Fluid friction- Friction that occurs as an
object moves through a fluid.
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Newton’s laws

Newton’s first law of motion- states
that an object at rest will remain at rest,
and an object moving at a constant
velocity will continue moving at a constant
velocity, unless it is acted upon by an
unbalanced force.
Inertia-The tendency of an object to resist
any change in its motion.( depends on
mass) ie. friction
Newton’s Laws
Newton’s second law of motionacceleration depends on the object’s mass
and on the net force acting on the object.
 Newton’s third law of motion- states
that if one object exerts a force on
another object, then the second object
exerts a force of equal strength in the
opposite direction on the first object.
Action-Reaction forces
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Gravity
The force that pulls objects toward each
other.
 Two factors affect the gravitational
attraction between objects: mass and
distance.

– The more mass an object has, the greater its
gravitational force.
– The farther apart two objects are, the lesser
the gravitational force between them.
Center of Mass
The center of gravity (mass)- is the point
where all the weight of the object can be
considered to be concentrated.
 To balance an object ( see saw) you would
need to find the center of mass
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Air and Gravity
Free Fall- The motion of a falling object
when the only force acting on it is gravity.
 Air resistance- The fluid friction
experienced by objects falling through the
air.
 Projectile- An object that is thrown.
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Weight v. Mass
Weight- The force of gravity on an object
at the surface of a planet.
 Mass- Amount of matter in an object
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