pass content standard 2.1 objects change their motion only when a net force is applied. laws of...

PASS Content Standard 2.1

Objects change their motion only whena net force is applied. Laws of motion areused to determine the effects of forceson the motion of objects.

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Motion - 12 min

• Earth rotates on its axis at 1,100 mph

• Earth orbits the Sun at 68,000 mph

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• The whole galaxy rotates at 490,000 mph

Two Dimensional World

Speed =distance

time

Speed =distance

time

A snail crawls 10 feet in 5 minutes.What is the speed of the snail?

=10 feet

5 minutes= 2 feet/min

Average speed =total distance

total time

Average speed =total distance

total time

A boy runs 1 mile in 6 minutes, rests for2 minutes, then walks 1 mile in 12minutes. What is his average speed?

=1 mile + 1 mile

20 minutes=

2 miles

20 minutes

Distance(meters)

Time (seconds)

is a vector quantitybecause it has bothspeed and direction.

Vectors - 12 min

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All these planes have the same speed.

How istheirvelocitydifferent?

The length of the line representsthe quantity (speed) and the arrowindicates the direction.

Add vectors head to tail.

Direction isindicated bycompass degrees

The magnitude of the speed isindicated bythe measuredlength (scale) of the line.

0o

90o

180o

270o

An airplane is flying 200mph at 50o. Wind velocityis 50 mph at 270o. Whatis the velocity of the plane?

0o

90o

180o

270o

Acceleration =Velocity(final) - Velocity(original)

time

A car traveling at 60 mph accelerates to 90 mph in 3 seconds. What is thecar’s acceleration?


time

A car traveling at 60 mph accelerates to90 mph in 3 seconds. What is thecar’s acceleration?

=90 mph - 60 mph

3 seconds

=30 mph

3 seconds

= 10 mph/second

A car traveling at 60 mph slams on the breaks to avoid hitting a deer. The car comes to a safe stop 6 seconds after applying the breaks. What is thecar’s acceleration?


time

A car traveling at 60 mph slams on the breaks to avoid hitting a deer. The car comes to a safe stop 6 seconds after applying the breaks. What is thecar’s acceleration?

=0 mph - 60 mph

6 seconds

=- 60 mph

6 seconds

= - 10 miles per hour per second

Acceleration toward thecenter of a circular path.

For an object to travel in acurved path, some force mustbe accelerating it toward the center of the circle.

Force providedby engine

Accelerationprovided by tires

What happens if the acceleratingforce is removed?

The objectmoves in astraight line.

An apparent forcethat appears only in rotating frames of reference.

This “false” forceappears to pushaway from thecenter of thecircular path.

If you are riding in the passengerseat of this car, what do you feel?

What's actually happening?

Aristotle and Newton had differentideas about forces and motion.

Aristotle's idea: For anobject to move at a constantspeed, a constant forcemust be applied.

Newton's idea: An objectmoving at a constant speedwill continue at that speedwithout additional forcebeing applied.

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ProduceNO

Motion

Produce Motion

Sliding - two solid surfaces rubbing against each other.

Rolling - an object rolling over a surface.

Fluid - an object moving through a fluid.

Newton’s Laws - 5 min


An object at rest will remain at rest, and a moving object will remain at a constant velocity unless acted on by unbalanced forces.

Force = mass X acceleration

F = Ma

For every action,there is an equaland oppositereaction.

Rockets - 6 min


Momentum - 8 min

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Does a long pendulum swingfaster than a short one?

Does a heavy pendulum swingfaster than a light one?

The total momentum ofany group of objectsremains the same unless acted on byoutside forces.

Elastic - occur when both momentumand kinetic energy are conserved.

Inelastic - occur when momentum is conserved, but kinetic energy is not.

M1V1 = M2V2

Before After

Colliding objects have same mass

Elastic Collision



Heavy object strikes light object

Elastic Collision



Light object strikes heavy object

Elastic Collision



Inelastic Collision

Colliding objects have same mass



Rollercoasters - 4 min


Units of Force are Newtons

Units of Distance are Meters

Newton Meters = Joules

Work - 2 min


A force of 200 Newtons is usedto move an object 10 meters.How much work is done?


W = Fd


W = Fd = (200 N)


W = Fd = (200 N)(10 meters)


W = Fd = (200 N)(10 meters) = 2000 Joules

Units of Work are Joules

Joules per second = Watts

Power is the rate at which work is done.

power - 2 min


A machine produces 250 joulesof work in 2 seconds. How muchpower is produced?


P = W / t


P = W / t = (250 joules)


P = W / t = (250 joules) / 2 sec


P = W / t = (250 joules) / 2 sec = 500 Watts

1 Horsepoweris equal to

745.56 Wattsor

550 ft lb/sec

The effort force isapplied to a machine.

The resistance force isapplied by a machine.

The number of times a machinemultiplies the effort force.

Work output Work input X 100

Inclined Plane

An 800 pound motorcycle is rolled up a 10 foot rampinto a pickup bed that is 3 feet off the ground.

Calculate input work.Calculate output work.Calculate efficiency %.

Work input = 10 ft X 800 lb = 8000 ft lb

Work output = 3 ft X 800 lb = 2400 ft lb

Work output Work input X 100

% Efficiency =

2400 ft lb 8000 ft lb X 100

0.3 X 100 = 30% Efficiency

Length Height =

Mechanical Advantage =

10 ft 3 ft =

3.33 mechanical advantage

Machines make work

easier or faster . . .

but machines NEVER

produce more work

than is put into them.

In fact, because of friction,

more work goes

into a machine

than comes out.

Climbing cars - 24 min


In 1868, a motion was passed in congress to abolish the U.S. Patent Office because all important discoveries had already been made.

Make work easier because the effort force moves over a greater distance than the resistance force.

Inclined Plane - 2 min


Force is multiplied since it is applied to a wide area and exerted over a small area.

Wedge - 2 min


Multiplies an effort force by acting through a long effort distance.

Screw - 1 min


A bar which movesfreely around a fixed position, or fulcrum.

Levers - 3 min


Three Parts of a Lever

Effort Force Resistance

Force

Fulcrum

The Fulcrum is betweenthe Effort Force and the Resistance force

Multiplies Effort Force and changes its direction

The Resistance is between the EffortForce and the Fulcrum

Multiplies the Effort Force but does not change its direction

The Effort Force is between the Resistance Force and the Fulcrum

Does not multiply the Effort Force anddoes not change itsdirection.

Does not multiply the Effort Force anddoes not change itsdirection.

What DOES it

do??

Direction of the Effort Force is changed.

Mechanical Advantage = 0

Direction of the Effort Force is not changed.

Mechanical Advantage = 1

Direction of the Effort Force is changed.

Mechanical Advantage is equal to the number of supporting ropes.

Pulleys - 1 min


A fixed pulleydoes not havea mechanicaladvantage.

Fixed pulleysonly changethe directionof the force.

A movable pulley has amechanicaladvantage.

The effort forceis in the directionof the movementof the resistance.

Two wheels of different sizes connected - the axle being the smaller wheel.

Wheel & Axle - 1 min


Worm Gear

Compound Machines - 4 min


pass content standard 2.1 objects change their motion only when a net force is applied. laws of...

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