Physics Final Exam
Terms in this set (244)
Which of the following problems would NOT be a part of physics?
Identifying all the bones in a human body.
A hypothesis is
an educated guess that has yet to be proven by experiment
A scientific fact is
close agreement by competent observers of observations of the same phenomena.
The difference between a hypothesis and a theory is that a hypothesis is
an educated guess whereas a theory has been tested successfully many times in many ways
A scientific hypothesis may turn out to be right or it may turn out to be wrong. If it is a valid hypothesis there must be a test for proving that it is
To test a scientific hypothesis you would
set up many experiments and look at the results
Which of the following statements is not true?
A good scientist is influenced by his or her likes and dislikes
Science, art, and religion do not contradict one another because
all three have different domains
Which of the following is a problem some people blame on technology?
A science teacher, an art instructor, and a religious studies teacher are arguing about their respective disciplines. Which of the following could be a claim that each teacher makes?
The goal of my discipline is to search for order and meaning in the world.
In solid conductors, electric current is the flow of
An ampere is a
unit of current
An example of a voltage source is
a dry cell, a generator, a car battery, rubbing a rubber rod with fur.
Compared to thin wires, electrical resistance in thick wires is
While you are standing on the ground in your running shoes, the greatest resistance between you and the ground is in
the running shoes
Alternating current is made by
alternating the direction of voltage of the power source
The net speed of electrons in a wire is about
Where do the electrons come from that produce heat and light in a light bulb?
The bulb's wire filament
In 2004, the number of electrons delivered to an average American home by an average power utility was
When we say an appliance "uses up electricity," we mean
Electron kinetic energy is changed into heat and other forms of energy
If you plug an electric toaster rated at 110 V into a 220 V outlet, current in the toaster will be
twice what it should be
Electric power is defined as
current times voltage
The current through a 5-ohm resistor connected to a 150-V power supply is
What is the resistance of a toaster that uses 5 A of current when connected to a 120-volt power source?
When connected to a 110-volt power supply, how much current is in a lightbulb that has a resistance of 220 ohms?
If you accidentally grabbed the prongs of partially plugged-in 120-V electrical plug on a day when your skin resistance was 130,000 ohms, how much current would pass through your body?
When plugged into a 120-V wall outlet, how much current is used by an electric blanket rated 140 W?
A light bulb is plugged into a 120-volt outlet and has a 0.7 A current in it. What is the power rating of the light bulb?
A 60 W light bulb and a 100 W light bulb are both rated at 120 B. Which light bulb has the larger resistance?
the 60-W light bulb
A 60 W light bulb and a 100 W light bulb are each connected to 120-V outlet. Which light bulb has more current in it?
the 100 W bulb
An electric heater is rated at 300 W for use in a 110-V circuit. The circuit breaker in the circuit can handle 12 A of current. How many heaters can be safely operated in the circuit?
A heater uses 21 A when connected to a 110 V line. If electric power costs 10 cents per kilowatt-hour in this location, the cost of running the heater for 13 hours is
A power line with a resistance of 9 ohms has a current of 80 A in it. The power dissipated in the line is
How much of each cycle of an alternating current will pass through a diode?
When input to a diode is AC, the output is a(an)
rough DC, off half the time
If you walk into a region of space and suddenly feel a force, the space is said to contain a
An electric field has
magnitude and direction
The direction of electric field lines shows the
direction of the force in a test positive charge.
Suppose you touch a negatively charged object to a metal sphere so that electrons move from the charged object onto the sphere. After the charge object is moved far away, electrons on the sphere will be
distributed evenly over the sphere's surface
A small, positively charged object near a positively charged sphere is moved closer to the sphere. The electrical potential energy of the small object
When an electron is brought near a negatively charged sphere, its potential energy increases. The reason this happens is that
work was done to bring the charges together
If two negative charges are held close together then released, the charges will
accelerate away from each other
A volt is a unit of
The electric field outside a Van de Graaff generator may be enormous, while inside the spherical dome, the electric field is
A woman's hair stands out when she is in contact with a charged Van de Graaff generator. The reason her hair stands out is because
like charges repel
A Van de Graaff generator is a machine that...
builds up high voltages.
After you rub a balloon on your hair, the balloon will likely be charged
to several thousand volts
A high beam of electrons accelerated from the back of your TV set to the screen. In order to make the beam hit the top of the screen, charged parallel plates create a vertical electric field. How will the top plate be charged?
Two parallel plates are oppositely charged. The left plate is negative and the right plate is positive. In which direction does the electric field point?
to the left.
The electric field lines between two charges curve in space. The direction at a particular point on a curved line is the direction of the
resultant vector of the field of the two charges at that point.
Electrical potential energy per charge is electric
Electric field lines between two oppositely charged parallel metal plates will be
straight lines, evenly spaced
The electric field in a certain region of space is 30 N/C. What is the force on a 2-C charged placed in that region?
If you use 17 J of work to push a charge into an electric field and then release the charge, as the charge flies past it's starting position, it's kinetic energy is
The charging of a capacitor is complete when
the potential difference between the capacitor plates is equal to the battery voltage
If you lift one load up two stories, how much work do you do compared to lifting one load up only one story?
Twice as much
If Nellie Newton pushes an object with twice the force for twice the distance, she does
four times the work
The unit of work is
The unit of power is the
Potential energy is the energy an object has because of its
The amount of potential energy possessed by an elevated object is equal to
the work done in lifting it
Kinetic energy of an object is equal to
one half the product of its mass times its speed squared
How much farther will a car traveling at 100 Km/s skid than the same car traveling at 50 km/s?
four times as much
Energy is changed from one form to another with no net loss or gain
When a car's speed triples, its kinetic energy
increases by nine times
Rockets are launched from an airplane in the forward direction of motion. The kinetic energy of the airplane will be
An object that has kinetic energy must have
A person on a roof throws one ball downward and an identical ball upward at the same speed. The ball thrown downward hits the ground with 140 J of kinetic energy. Ignoring air friction, with how much kinetic energy does the second ball hit the ground?
If an object has kinetic energy, then it also must have
The ratio of output force to input force of a simple machine is called the
The ratio of useful work output to total work input is called the
About how efficient is a typical gasoline-burning car engine?
Consider molecules of hydrogen gas and molecules of heavier oxygen gas that have the same kinetic energy. The molecules with the greater speed are
How many joules of work are done on a box when a force of 25 N pushes it 3 m?
How much work is done on a 60-N box of books that you carry horizontally across a 6 m room?
How much work is done on a 20-N crate that you lift 2 m?
It takes 80 J to push a large box 8 m across a floor. Assuming the push is in the same direction as the move, what is the magnitude of the force on the box?
If Kelly the skater's speed increases so he has three times the momentum, then his kinetic energy increases by
A pulley has two supporting strands. In order for it to lift a load 1 meter, the person pulling will have to pull a distance of
A machine puts out 100 watts of power for every 1000 watts put into it. The efficiency of the machine is
Mechanical energy can be in the form of
both kinetic and potential energy
When a worker shovels coal into the furnace of a train engine, energy is released from the coal as heat. The heat is used to make steam, which is then used to turn the wheels of the engine. Living cells can also be thought of as machines. What biological process uses combustion to release energy from molecules so that cells can do work?
You use a pulley to lift your bike to the ceiling for winter storage. When you bought the pulley, the salesman claimed that the pulley has a mechanical advantage of 10. While lifting the bike now has an actual mechanical advantage of 3. What is its efficiency?
While using a simple 2-piston hydraulic system, you apply a force of 10 N on the first piston to push it down 1 meter. You watch the second piston move 100 N crate up a distance of 5 centimeters. What is the efficiency of the hydraulic system?
A measure of how fast something is moving, always measured in terms of a unit of distance divided by a unit of time, the distance covered per minute
One possible unit of speed is
miles per hour, light years per century and kilometers per hour
When you look at the speedometer in a moving car, you see the car's
Acceleration is defined as the CHANGE in
velocity divided by the time interval
Suppose you are in a car that is going around a curve. The speedometer reads a constant 30 miles per hour. Which of the following is NOT true?
Your velocity is constant
A car starts from rest and after 7 seconds it is moving at 42 m/s. What is the car's average acceleration?
In the absence of air resistance, objects fall at constant
A ball is thrown upwards and caught when it comes back down. In the absence of air resistance, the speed of the ball when caught would be
the same as the speed it had when thrown upwards
Suppose an object is in free fall. Each second the object falls
a larger distance than in the second before
If you drop a feather and a coin at the same time in a tube filled with air, which will reach the bottom of the tube first?
The hang time for most athletes is
less than 1 second
Suppose you take a trip that covers 180 km and takes 3 hours to make. Your average speed is
Suppose a car is moving in a straight line and steadily increases its speed. It moves from 35 km/h to 40 km/h the first second from 40 km/h to 45 km/h the next second. What is the car's acceleration?
5 km/h s
When something falls to the ground, it accelerates. This acceleration is called the acceleration due to gravity and is symbolized by the letter g. What is the value of g in Earth's surface?
about 10 m/s^2
A car accelerated at 2 m/s^2. Assuming the cat starts from rest, how much time does it need to accelerate to a speed of 20 m/s?
If a freely falling object were somehow equipped with a speedometer, it's speed reading would increase each second by
about 10 m/s
If a ball were equipped with a speedometer and allowed to fall freely on a planet where the acceleration due to gravity is 23 m/s^2, the reading on the speedometer would increase each second by
A freely falling object starts from rest. After falling for 6 seconds, it will have a speed of about
A freely falling object starts from rest. After falling for 1 second, it will have a speed of about
If you drop a feather and a coin at the same time in a vacuum tube, which will reach the bottom of the tube first?
neither- they will both reach the bottom at the same time.
The vertical height attained by a basketball player who achieves a hang time of a full one second is about
Suppose a jumper claims a hang time of 2 seconds. Then that jumper must be able to jump a vertical distance of
A pencil lies on your desk. If the Earth is moving around the sun at a speed of 30 km/s how fast is the pencil moving relative to the desk? How fast is the pencil moving relative to the sun?
0 km/s ; 30 km/s
Acceleration is defined as
the rate at which velocity itself changes
A 15-N force and a 45-N force act on an object in opposite directions. What is the net force in the object?
What is the maximum resultant possible when adding a 2-N force to an 8-N force?
What is the minimum resultant possible when adding a 5N force to an 8N force?
Equilibrium occurs when
all the forces acting on an object are balanced, the sun of the +x forces in an object equals the sum of the -x forces, the net force on an object is zero, the sum of the upward forces equals the sum of the downward forces
A girl whose weight is 500 N hangs from the middle of a bar supported by two vertical strands of rope. What is the tension in each strand?
The weight of a person can be represented by a vector that acts
straight down, even if the person is standing on a hill
A barge is being pulled along a canal by two ropes that make equal angles with the direction in which the barge points. Assuming the two pulls on the barge are equal, i. what direction does the barge move?
It moves straight ahead and it moves in the direction of the resultant vector
A clothesline is stretched between two trees. A tire bangs in the middle of the line and the two halves of the line make equal angles with the horizon. The tension in the line is
more than half the tire's weight
You are helping your aunt move a piano in wheels from one room to another. When you push the piano horizontally it moves at constant speed. What can you say about the piano?
it is in dynamic equilibrium?
Which has more momentum, a large truck moving at 30 miles per hour or a small truck moving at 30 miles per hour?
the large truck
compare to a sports car moving at 30 miles per hour the same sports car moving at 69 miles per hour has
twice as much momentum
If the momentum of an object changes and its mass remains constant
it is accelerating(or decelerating) there for is a force acting on it, its velocity is changing
The momentum of an object is equal to
impulse acting on it
The reason padded dashboards are used in cats is that they
increase the time of impact in a collision
A table tennis ball launcher is fired. Compared to the force on the ball, the force on the launcher is
A collision is considered elastic if
after the collision the objects have the same shape as before the collision, there is no lasting deformation, the objects don't stick together, the objects that collide don't get warmer
A table tennis ball launcher is fired. Compared to the impulse on the ball the impulse on the launcher is
Suppose a girl is standing on a pond where there is no friction between her feet and the ice. In order to get off the ice she can
throw something in the direction opposite to the way she wants to gk
Which of the following has the largest momentum?
A pickup truck traveling down the highway
A freight train rolls along a track with considerable momentum. If it were to roll at the same speed but had twice as much mass, it's momentum would be
The force that accelerated a rocket into outer space is exerted on the rocket by
the exhaust gases
If all people, animals, trains, and trucks all over the world began to walk or run towards the east then
Earth would spin a bit slower
Suppose an astronaught in outer space wishes to toss a ball against a very massive and perfectly elastic concrete wall and catch it as it bounces back. If the ball is as massive as the astronaut thwn
the astronaut will never catch the first bounce
A table tennis moving forward with 5 units of momentum strikes and bounces backward off a heavy bowling ball that is initially at rest and free to move. The bowling ball is set in motion with a momentum of
more than 5 units
While roller skating, granny collided with her ring grandson Ambrose who is at rest. Ignoring any friction effects, Ambrose's speed after the collision will be greatest when
he and granny make a bouncing collision, each going in opposite direction
A small economy car (low mass) and a limousine (high mass) are pushed from rest across a parking lot, equal distances with equal forces. The car that receives the greater impulse is the
A 2 kg ball is thrown at 3 m/s. What is the ball's momentum?
6 kg m/s
A ball is moving at 6.0 m/s and has a momentum of 24.0 kg m/s. What is the balls mass?
A 5.0 kg chunk of putty moving at 10.0 m/s collides with and sticks to a 7.0 kg bowling ball that is initially at rest. The bowling ball with its putty passenger will then be set in motion with a momentum of
50.0 kg m/s
A piece of putty and a rubber ball have the same mass. If your drop them from the same height, which object will produce a greater impulse and why?
The rubber ball will produce a greater impulse because it will bounce.
a truck travels north with momentum of 2,600 kg km/s and a motorcycle heads west with a momentum of 1500 kg km/s. The motorcycle hits the truck. If the two vehicles collide and then stick together, what is the momentum and direction of travel?
The vehicles travel with a momentum of 3000 kg km/s in the NW direction
The astronomer Copernicus publicly stated in the 1500s that Earth
revolves around the sun
Friction is a force that always acts
opposite to an object's motion
The law of inertia states that an object
will continue moving at the same velocity unless an outside force acts on it, will continue moving in a straight line unless and outside force acts on it, that is not moving will never move unless a force acts on it, at rest will remain at rest unless acted on by an outside force
The law of inertia applies to
both moving and nonmoving objects
After a cannonball is fired into frictionless space, the amount of force needed to keep it going equals
zero, since no force is necessary to keep it moving
If the force of gravity suddenly stopped acting on the planets they would
move in straight lines tangent to their orbits
A sheet of paper can be withdrawn from under a container of milk without toppling it if the paper is jerked quickly. The reason this can be done is that
the milk carton has inertia
The force required to maintain an object at a constant speed in free space is equal to
An object following a straight line path at constant speed
has zero acceleration
comes from microscopic bumps that act as obstructions to the objects motion, is the name given to the force acting between surfaces sliding past one another, acts in a direction that opposes the motion of an object
One object has twice as much mass as another object. The first object also has twice as much
Compared to its weight on Earth, a 10 kg object on the moon is
Compared to its mass on Earth, the mass of a 10 kg object on the moon is
An object weighs 30 N on Earth. A second object weighs 30 N on the moon. Which has the greater mass?
The one on the moon
Which of the following is NOT true about Aristotle's concept of violent motion?
Violent motion is thought to be either straight up or straight down
You and a friend are jumping on a trampoline. Why does Earth, which is rapidly orbiting around the sun, not move under your feet when you jump?
Newton's first law holds that your body moves along the with Earth because it is not compelled to change its motion by an unbalanced force.
How does acceleration of an object change in relation to its mass?
It is inversely proportional.
The acceleration produced by a net force on an object is
inversely proportional to the mass of an object, directly proportional to the magnitude of the net force, in the same direction as the net force
When an object reaches terminal velocity its acceleration is
A heavy person and a light person parachute together and wear the same size parachutes. Assuming they open their parachutes at the same time, which person reaches the ground first?
the heavy person
A 10 kg brick and a 1 kg book are dropped in a vacuum. The force of gravity on the 10 kg brick is
10 times as much as the force in the 1 kg book
When a woman stands with two feet on a scale the scale reads 280 N. When she lifts one foot the scale reads
A book weighs 4 N. When held at rest in your hands the net force on the book is
An apple weighs 1 N. The net force on the apple when it is in free fall is
A girl pulls on a 10 kg wagon with a constant force of 20 N. What is the wagons acceleration?
An object has a constant mass. A constant force on the object produces constant
A force of 3 N accelerates a mass of 3 kg at the rate of 1 m/s^2. The acceleration of a mass of 6 kg acted upon by a force of 6 N is
A push in a 1kg brick accelerates the brick. Neglecting friction, to equally accelerate a 10 kg brick one would have to push
with 10 times as much force
A rock is thrown vertically into the air. At the very top of its trajectory the net force on it is
Pressure is defined as
force per area
The reason a tennis ball and a solid steel ball will accelerate at the same rate, in the absence of air resistance, is that
the ball with the larger force also has the larger mass
The terminal speed for a person parachuting (with the chute open) is about
As a care package falls from a high-flying stationary helicopter, it's velocity increases and its acceleration
If you pull horizontally on a desk with a force of 150 N and the desk doesn't move, the friction force must be 150 N. Now if you pull with 250 N so the desk slides at constant velocity, the friction force is
When the angle of an incline with a block resting on it increases, the normal support force
A block is at rest on an incline. The force of a friction necessary to prevent the block from sliding increases when the incline is
Consider a ball rolling down the decreasing slope inside a semicircle bowl (the slope is steep at the top rim, gets less steep toward the bottom, and is zero (no slope) at the bottom). As the ball rolls from the rim downward toward the bottom, it's rate if gaining speed
A speeding truck locks its breaks and it skids to a stop. If we he trucks total mass were doubled, it's skidding distance would be
If the force acting on a cart doubles, what happens to he carts acceleration
suppose a cart is being moved by a force. If suddenly a load is dumped into the cart so that the carts mass doubles, what happens to the carts acceleration?
You are on a frozen pond, and the ice starts to crack. If you lie down on the ice and begin to crawl, this will
decrease the pressure on the ice
A 20 N falling object encounters 4 N of air resistance. The magnitude of the net force in the object is
A sports car has a mass of 1500 kg and accelerates at 5 meters per second squared. What is the magnitude of the force acting on the sports car?
A low truck exerts a force of 2000 N on a car, accelerating it at 1 m/s/s. What is the mass of the car?
A jet has a mass of 40,000 kg. The thrust for each of four engines is 20,000 N. What is the jet's acceleration when taking off?
You pull horizontally on a 50 kg crate with a force of 450 N and the friction force on the crate is 250 N. The acceleration of the crate is
How much force is needed to accelerate a 4.0 kg physics book to an acceleration of 2.0 m/s^2?
A jumbo jet cruises at a constant velocity when the total thrust of the engines on the jet is 50,000 N How much air resistance acts on the jet?
A 6 N falling object encounters 6 N of air resistance. The magnitude of the net force on the object is
If a truck has ten times the mass of a car and the two vehicles are pushed with an equal force, you would expect the acceleration of the truck to be
1/10 times that of the car
Whenever an object exerts a force on another object, the second object exerts a force of the same magnitude, but in the opposite direction to that of the first object.
A high school student hits a nail with a hammer? During the collision, there is a force
on the nail and also on the hammer
Forces always occur
A player catches a ball. Consider the action force to be the impact of the ball against the players glove. What is the reaction to this force?
The force the glove exerts on the ball
A player hits a ball with a bag. The action force is the impact of the bar against the ball. What is the reaction to this force?
The force of the ball against the bat
An unfortunate bug splatters against the windshield of a moving car. Compared to the force of the car in the bug, the force of the bug on the car is
A large truck and a small car traveling at the same speed have a head on collision. The vehicle to undergo the greater change in velocity will be
the small car
Earth pulls on the moon, and similarly the moon pulls on the Earth. This is evidence that the
Earth and moon are simply pulling on each other and Earth's and Moon's pulls comprise and action-reaction pair
Bronco the sky diver falls toward the Earth. The attraction of Earth on Bronco pulls him down. The reaction to this force is
Bronco pulling on the Earth
A force is exerted on the fires of a car to accelerate the car along the road. The force is exerted by the
A rocket is able to accelerate in the vacuum of space when it fires its engines. The force that propels the rocket is the force
of the exhaust gases on the rocket
A karate chop delivers a blow of 2300 N to a board that breaks. The force that acts on the hand during this feat
is 2300 N
A woman weighing 550 N sits on the floor. She exerts a force on the floor of
Two people pull on a rope in a tug of war. Each pulls with 400 N or force. What is the tension in the rope?
Suppose two people, one having three times the mass of the other, pull on opposite sides of a 20 meter rope while on frictionless ice. After a brief time, they meet. The more massive person slides a distance of
Suppose you accidentally drive into a tree. Which of the following correctly describes the interaction between your cat and the tree?
The car and the tree mutually exert equal and opposite forces on each other
If your car runs out of gas, why can't you push on the car's windshield from the inside to move it?
In order for the car to move? a force must be exerted by the car on the ground.
When representing velocity as a vector
the direction of the arrow shows the direction of motion, the length of the arrow represents the speed, and the length of the arrow is drawn to a suitable scale
In order to find the components of a vector, you should
draw the vector with correct magnitude and orientation, measure the sides of the rectangle, draw a rectangle so that the vector is the diagonal
Which of the following would NOT be a projectile?
a cannonball rolling down a slope
In the absence of air friction, the vertical component of a projectiles velocity doesn't change as the projectile moves
At the instant a ball is thrown horizontally with a large force, an identical ball is dropped from the same height. Which ball hits the ground first?
neither they both hit the ground at the same time
At what part of a path does a projectile have minimum speed?
At the top of its path
A cannonball is launched from the ground at an angle of 30 degrees above the horizontal and a speed of 30 m/s. ideally (no air resistance) the ball will land on the ground with a speed of
A projectile launches horizontally hits the ground in 0.8 seconds. aid it has been launched with a much higher speed in the same direction; it would have hit the ground (neglecting Earths curvature and air resistance) in
A cannonball is launched horizontally from a tower. if the cannon has a barrel velocity of 60 m/s, where will the cannonball be 1 second later?
60 meters down range
after rock that is thrown straight up reaches the top of its path is starting to fall back down its acceleration is
The same as when it was at the top of its path
José can jump vertically 1 m from his keyboard when it is at rest when the skateboard is moving horizontally José can jump
what is the resultant of a three unit factor in a four unit factor at right angles of each other
in chapter two you learned about hang time, the time a jumpers feet off the ground in a vertical jump. if the jumper runs horizontally and has the time the same vertical component of take off velocity, hang time will be
at the instant a ball is thrown horizontally with large force an identical ball is dropped from the same height which ball hits the ground first
neither they both hit the ground at the same time
hey cannonball is fired at some angle into the air in the first second it moves 5 m horizontally assuming it doesn't hit the ground and air resistance is negligible how far does it move horizontally in the next second
A ball is thrown straight upward at 10 m/s I Deleigh the ball will return to the throwers hand the speed of
A canon with a barrel velocity of 140 m/s launches the cannonball horizontally from a tower. neglecting air is this dense how far vertically with the cannonball have fallen after four seconds
calculate how much rest and object contains you multiply
it's mass times the speed of light required
according to the well known equation energy equals mass times the speed of light squared
mass and energy are related
relativity equations for time length in momentum hold true for
every day low speed's and relativistic speeds
correspondence principal says that
any new theory must agree with the old correct theory
if Einstein's equations of special relativity are valid say must
reduced to newton's equations when the speed is small, give correct answers for speed is much less than the speed of light, and agree with the correct results of newtons equations
in physics lab you conduct an experiment to evaluate the difference that changing a particle speed makes on its momentum. you send an electron at a speed of 99% that of light through a chamber that has a magnetic field inside and noticed that the electrons path curve sharply. if you send an electron at a speed of 99.9% of the speed of light through the same chamber you would notice
a smaller curve in the path the electron takes
principle of ________ states that local observations made in an accelerated frame of reference cannot be distinguished from observations made in a Newtonian gravitational field
you are communicating with aliens on Jupiter and Saturn. when you send the light beam message to your friend on Jupiter you receive a message from your friend on Saturn, you realize that the light messages become curved when they pass the sun. what would be the sum of the angles in the triangle formed by the paths your message takes
A number larger than 180°
during a solar eclipse you have the opportunity to observe stars around the periphery of the sun with a telescope which of the following is an observation that you would expect to make
The starlight is deflected
in General relativity gravitational red shift is caused by
The slowing of clocks do to lower gravitational potential energy
to a person who is inside spaceship moving close to the speed of light a meter stick hell horizontally inside the ship looks
just the same as always
two outside observers objects traveling at relativistic speeds look
spaceship was his past is space station at close to the speed of light. an observer on the station measures the length of a spaceship as less than when the ship is at rest, and an observer on the spaceship measures the length of the space station as
Less than when the ship isn't moving
we are actually looking into the past when we look at
starlight and our physics book
in some reference frame in the universe you right now are traveling at a speed close the speed of light
A friend is writing on the back of a truck that is going away from you at 25 km/h after the truck passes your friend throws a ball toward you at 55 km/h relative to her how fast is the ball going relative to you
as a blinking light source approaches you add an increase in speed the frequency of the flash
compared to the time kept on earth there is a physical slowing of time when you travel at
every day low speeds and relativistic speeds
when we move through space just a little bit we are moving
mostly through time and only a little bit through space
suppose an alien invites you to take a trip on her spaceship if you travel at the speed of light you would be
traveling through space but not through time
and observer is moving at half the speed of light in a direction perpendicular to a ride of blanks L the observer will measure the length of the rod to be
equal to L