forces. what is a force? a force is a push or a pull. forces do not have mass nor do they occupy a...
TRANSCRIPT
FORCES
What is a force?
• A force is a PUSH or a PULL.• Forces do not have mass nor do
they occupy a space.• Forces can
– tear, bend, twist, or stretch an object.– Change the direction of the motion
• Measured in Newtons (N)
2 main types of forces
• Contact forces– A force between two objects in direct contact
with one another.Frictional
• Non-Contact forces– Forces that can act on objects at a distance
and between two objects which are not in direct contact with one another.
MagneticGravitational
Gravitational Force
• Pulls objects towards the center of the earth• Objects exert a force of attraction on all objects
around it.– The force may be small that we can’t feel it.
• The larger the mass, the stronger the gravitational force– The sun’s gravitational force pulls smaller bodies
towards it
• The closer the two objects are, the stronger the gravitational force
Gravitational force
• Objects fall to the ground at the same rate, regardless of their mass in the absence of air
• Overcoming gravity:– Energy is needed to overcome gravity– More energy if you’re going against it– Less energy if you’re going towards it.
Gravitational energy in our daily lives
Frictional Force
• A force that opposes motion. • Produced when two surfaces are in
contact with each other• Can cause an object to move slower• More friction is exerted if the object’s
mass is great• Surfaces play a role in the amount of
friction generated
Frictional Force
• Types of friction– Sliding
• Two solid objects with one object sliding over the other• snowboarding
– Rolling• When a circular object rolls over a surface• cycling
– Fluid• Involves a solid object moving through a wet or fluid (liquid or
gas)surface• Parachuting, wakeboarding
Infer the friction generated in the given
pictures
Frictional energy
• Energy is required to overcome friction.• How much energy is needed to
overcome friction over smoother surfaces?
• How much energy is needed to overcome friction over rougher surfaces?
• When is frictional energy beneficial? When is frictional energy harmful?
Frictional energy in our lives
Magnetic Force
• A force of attraction that pulls unlike poles.
• A force of repulsion that pushes like poles.
• A MAGNET attracts magnetic materials, which include those made up of Iron, steel, cobalt and nickel
Magnetic force
• A stronger magnet exerts a stronger force of attraction– The material may move faster– A stronger force is needed to
overcome a stronger magnet
N S N S
Magnetism in our daily lives
The PENDULUM
String
Metal ball
gra
vity
The PENDULUM
• Found in clocks; has a weight and a string
• Air resistance (frictional force) and gravity affect the motion of the pendulum
• The length of the string also affects the time for the pendulum to complete its swings