chapter 13 – forces in motion
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Chapter 13 – Forces in Motion. Types of Motion. Constant Motion – motion that is constant and steady. Types of Motion. Variable Motion – motion that moves in many directions and at many speeds. Types of Motion. Periodic Motion – back and forth steady movement. Types of Motion. - PowerPoint PPT PresentationTRANSCRIPT
Chapter 13 – Forces in
Motion
Types of MotionConstant Motion – motion that is constant and steady
Types of MotionVariable Motion – motion that moves in many directions and at many speeds
Types of MotionPeriodic Motion – back and forth steady movement
Types of MotionCircular Motion – movement in circles
Types of MotionVibrational Motion – movement that is quick, back and forth vibrations
Speed• The distance an object travels
in a certain amount of time.• To find the speed divide the
distance and the time it took to go that distance
• S = D/T• Sammy the Snail
VelocityDescribes the speed and direction of an object’s motion.Example: The plane is moving west at 300mph.
Speed and Velocity
Point of ReferenceMotion measured as a relationship between two objects.
Referencepoint
Force• A push or a pull that acts
on an object.• Forces can make a moving
object speed up, slow down, or change directions.
Gravity• The force of attraction
between two objects causing them to have weight.
• Examples• Apple falling out of a tree.• Skydiver landing on the
ground.
Magnetism• A force that pushes and
pulls on other objects• Push – two north poles will
push away from each other• Pull – a north pole and a
south pole will pull toward each other
Electricity• All objects that are
electrically charged will exert forces on each other.
• Oppositely charged objects are attracted to each other.
• Objects with the same chare are repelled, and move away from each other
Friction• The force between moving parts that tends to
slow them down.
Magic School Bus – Plays Ball
Work• Work is done when a force moves an object.• If the force does not make the object move,
then no work has been done• Work is done only when the object moves
Scientific Definition
Formula
Work(Joules)
Energy used when a force moves an object
Work = force x distance
Power• The rate at which work is done.• Walking up a hill and running up the same hill
take the same amount of work. Since running up the hill is faster than walking, the amount of power needed to run is greater.
Scientific Definition
Formula
Power(Watts)
Rate at which work is done
Power = work/time
Newton’s 1st Law of Motion• An object at rest stays at rest until a force
acts on it. An object moving at a constant speed will continue to move in a straight line and at a constant speed until a force acts on it.
Inertia• The tendency of an object
to resist any change in motion
• The physical property that keeps an object moving after the accelerating force is gone.
Newton’s 2nd Law of Motion• Acceleration is produced when a force acts
on a mass. The greater the mass (of the object being accelerated) the greater the amount of force needed (to accelerate the object).
Acceleration• The rate at which the
velocity of an object changes over time.
Newton’s 3rd Law of Motion• For every action there is an equal and
opposite re-action.
Air Resistance• The force that acts to slow
down any object moving through air.
Pulley• A pulley consists of a rope or
cable that runs through a grooved wheel.
• Makes work easier by changing the direction of the force
• Examples – flagpole, window blinds
Wheel and Axle• A wheel and axle is made
up of a circular object and a shaft.
• Examples – doorknob, bicycle wheel
Lever• A lever is a stiff bar rotating
around a fixed point called a fulcrum.
• Makes work easier by changing the direction of a force.
• Examples – hammer, shovel
Inclined Plane• An inclined plane consists
of a flat surface with one end higher than the other.
• Examples – wheelchair ramp, playground slide
Screw• An incline planed wrapped
around a center rod• Examples – base of jar lid,
light bulb base
Wedge• A wedge is two inclined
planes placed back to back• Examples – knife, axe, fork,
nail, doorstop