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47 Cards in this Set

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Inertia
tendency of an object to resist a change in motion
Inertia depends on the object’s mass.
More Mass=More Inertia=Harder to Start/Stop
Less Mass=Less Inertia=Easier to Start/Stop
Newton's First Law
An object at rest will stay at rest and an object in motion will stay in motion until acted on by an unbalanced force.
Force
push or pull that can cause an object accelerate
Units-kg•m/s2
Force is a vector quantity
Net Force
combination of all forces that act on an object
-Symbol-<sum>F
Unbalanced Force
An unequal force that changes an object’s motion
(<sum>F!=0)
Balanced Force
Equal forces acting on an object in opposite directions, will not cause a change in motion. (<sum>F=0)
Two Types of Balanced Forces
-Static/Mechanical Equilibrium: objects at rest (<sum>F=0)
-Normal Force/Support Force
-Dynamic Equilibrium: object moving at constant velocity (<sum>F=00
-Moving Force=Resisting Force
Newton's Second Law
Force=Mass x Acceleration
-Mass and acceleration are inversely proportional
-Force and acceleration are directly proportional
Newton's Third Law
For every action there is an equal but opposite reaction
Why don’t action and reaction forces cancel each other out as a balanced force?
Forces are added together to get a balanced force only if the force is acting on the same object. Action and reaction forces are applied to different objects.
Motion
An object is considered in motion when its distance from another object changes
Reference Point
Object or place used for comparison to determine if an object is in motion
Speed
Distance object travels in time
Speed=Distance/Time
Velocity
Speed in a given direction
Acceleration
Rate at which the velocity changes
(Final Velocity-Initial Velocity)/Time
3 types of acceleration
Increase (positive)
Decrease (negative)
Change Direction (centripetal acceleration)
Aristotle
-384-322 BC
-Studied under Plato
-Philosopher and scientist
-Tutor to Alexander The Great
-One of first to look at physical world of science
-Started school called Lyceum
-Natural Motion-object’s natural state is rest
-Unnatural Motion-force required causing motion
-Heavier objects fall faster than lighter objects
-Based work on observation and logic
Galileo
-Late 1500’s-early 1600’s
-Went to University of Pisa
-Dropped out which allowed him time to research physics
-Started experiments with motion
-Was a teacher at colleges
-Became advocate of Copernicus
-In 1609 was first to use telescope
-In 1630’s wrote a book called Dialogue
-Went to jail
-Went blind because he looked at the sun too much
-Once an object is in motion no force is needed to keep it in motion
-Force needed to change the motion of an object
-Inertia-tendency of an object to resist a change in motion
-All object fall at the same rate
-Based work on experimentation
Projectile Motion
An object upon which the only force acting on it is gravity
Types of Projectiles
An object dropped from rest
An object which is thrown vertically upwards
An object is which thrown upwards at an angle is also a projectile
what are the velocities of projectiles?
Highest velocity when released
As objects travel upward gravity slows object to 0
As object travels downward gravity increases velocity
Highest velocity when object hits ground
What are the components of a projectile?
The path of a projectile has a horizontal component and a vertical component.
-They are independent of each other
-The projectile moves forward because of inertia
-The projectile accelerates downward because of gravity
Work
Work is done on an object when a force is exerted on an object that causes the object to move some distance
What two things must be controlled in order for work to be done?
No work without motion
No work without force in the same direction
Formula for work
Work=Force•Distance
Power
The rate at which work is done
Formula for power
Power=Work/Time
What 3 things do machines do to make work easier?
Change the amount of force you input
Change the distance over which you exert the force
Change the direction of the way you apply force
Why doesn't the total work change?
If a machine allows you to apply a smaller force the distance will increase
If a machine reduces the distance the force will increase
If a machine allows you to apply a force in a different direction it doesn’t change how much force you have to apply or how far you move it
What is the mechanical advantage?
The number of times a force exerted on a machine is multiplied by the machine
Formula for mechanical advantage
M.A.=Output Force÷Input Force
What happens if M.A.>1?
If M.A.>1 machine multiplies the input force
What happens if M.A.<1?
If M.A.<1 machine multiplies the input distance
What happens if M.A.=1?
If M.A.=1 changing direction
Efficiency
Compares output work to input work (%)
Formula for efficiency
Efficiency=Output work÷Input Work•100
Can efficiency be greater or equal to 100?
No
Friction
the resistive force that opposes motion or attempted motion of an object past another with which it is in contact or through a fluid
What 2 factors does friction depend on?
Kinds of Surfaces
Pressure Between Surfaces
Surface Area DOES NOT Affect Friction
3 types of friction
Sliding
Fluid
Rolling
Gravity
a force that pulls objects towards the earth
Rate of acceleration
9.81 m/s
Terminal velocity
highest velocity that an object reaches
Mass
quantity of matter in an object
Weight
the gravitational force exerted on an object by the nearest most massive object
Universal law of gravitation formula
F(grav.)=G•m-sub1•m-sub2/d-squared
What are the 6 simple machines?
Lever
Pulley
Inclined Plane
Wheel & Axel
Wedge
Screw