why does time pass more slowly for observers traveling at high speeds or near a massive body
TRANSCRIPT
Why does Time pass more slowly for observers traveling at high speeds or near a massive body.
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 - 4 min
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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
0o
90o
180o
270o
0o
90o
180o
270o
0o
90o
180o
270o
0o
90o
180o
270o
Acceleration =Velocity(final) - Velocity(original)
time
Acceleration =Velocity(final) - Velocity(original)
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
Acceleration =Velocity(final) - Velocity(original)
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?
An apparent forcethat appears only in rotating frames of reference.
This “false” forceappears to pushaway from thecenter of thecircular path.
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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Forces & motion - 6 min
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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
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An object at rest willremain at rest, and amoving object willremain at a constantvelocity unless actedon by unbalanced forces.
Force = mass X acceleration
F = Ma
For every action,there is an equaland oppositereaction.
Rockets - 6 min
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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
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Colliding objects have same mass
Elastic Collision
Heavy object strikes light object
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Elastic Collision
Light object strikes heavy object
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Elastic Collision
Inelastic Collision
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Colliding objects have same mass
Rollercoasters - 24 min
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Units of Force are Newtons
Units of Distance are Meters
Newton Meters = Joules
Units of Work are Joules
Joules per second = Watts
Power is the rate at which work is done.
Work & Power - 15 min
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power - 2 min
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1 Horsepoweris equal to
745.56 Wattsor
550 ft lb/sec
Climbing cars - 24 min
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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
Da Vinci - 8 min
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Work is made easier because the effort force moves over a greater distance.
Inclined Plane - 2 min
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Force is multiplied since it is applied to a wide area and exerted over a small area.
Wedge - 2 min
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Multiplies an effort force by acting through a long effort distance.
Screw - 1 min
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A bar which can movefreely around a fixed position, or fulcrum.
Levers - 3 min
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The Fulcrum is betweenthe Effort Force and the Resistance force
Multiplies Effort Force and changes its direction
The Resistance is between the Effort Force and the Fulcrum
Multiplies the Effort Force butdoes not change its direction
The Effort force is between the Resistance Force and the Fulcrum
Does not multiply the Effort Force
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
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A fixed pulleydoes not havea mechanicaladvantage.
Fixed pulleysonly changethe directionof the force.
A movable pulleydoes have 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
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Worm Gear
Compound Machines - 4 min
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