Physics Final
Shown here are the results of Young's experiment demonstrating the interference of light. What does the observation of an interference pattern show about the nature of light?
It shows that light consists of waves.
In 1989, Ann Transom broke the U.S. women's record for a 24 h run by covering a distance of 143 miles. What was her average speed?
143 miles / 24 hours run = 5.96 miles per hour
How far can a spark jump in dry air if the electric potential difference is 6.00 x 10^5 V? (This is the reason why high-voltage sources are surrounded by a vacuum or an insulating fluid.)
20 cm (60000 / 3000)
To be eligible to enter a particular marathon that covers a distance of 26.2 miles, a runner must be able to finish in less than 6 h. What minimum average speed must be maintained to accomplish this?
26.2 miles / 6 hours = minimum avg. speed of 4.37 mph
Starting at 9 A.M., you hike for 3 hours at an average speed of 3 mph. You stop for lunch from noon until 4 P.M. What is your average speed over the interval from 9 A.M. to 4 P.M.?
9 miles totally traveled / 7 hours total = 1.29 avg. speed
How much work does a 9 V battery do in pushing 9 mC of charge through a circuit containing one lightbulb?
9 x 9 = 81 mJ
Your plan was to be on the road by 8 A.M. but you did not leave the garage until 10 A.M. You then drove with the cruise control set at 45 mph until stopping at noon. What was your average speed over the time interval from 8 A.M. to noon?
90 miles totally traveled / 4 hours total = 22.5 mph avg. speed
If the weight of an object with mass m is given by W = mg on Earth's surface, what will its weight be inside an airplane at an altitude of 35,000 feet?
It will be slightly less because g is somewhat smaller at that height.
How would a compass needle align itself in the magnetic field shown in this figure?
It would align itself along the magnetic field lines circling the wire, with the north pole of the compass pointing clockwise.
In this figure a time sequence shows one complete cycle for the vibration of an object on a spring. How would the equilibrium position of the object change if its mass were increased?
It would go down.
Which of the following is true of the rock in this figure as it falls after being dropped from a great height?
Its speed increases until it reaches a constant value, but its acceleration decreases gradually to zero.
What results when the net force on an object increases?
Proportionally increased acceleration.
When an object is moving in a circle, but it is not held to the center by a tangible connection like a string, what provides the centripetal force?
some force such as friction or gravity
Which of these is NOT a vector quantity?
speed
In which of these media can a transverse mechanical wave travel?
stretched rope
Where did Thomson's model place electrons in the atom?
studded throughout a positively-charged material
The net force always points in the same direction as which of the following?
the acceleration
What is the unit of electric current?
the ampere
Which of the following is caused by magnetic force on charged particles?
the aurora borealis and aurora australis
When something is thrown over large distances (on Earth), what new factor comes into play?
the curvature of the Earth
What is wavelength?
the distance between identical positions on adjacent wave pulses
When an object is hanging on the end of a vertical spring, what is the amplitude of the oscillating up-and-down motion?
the distance the object travels from its equilibrium point to either its lowest point or highest point
What two facts did Newton need to be able to calculate the acceleration of the Moon?
the distance to the Moon and the time it takes the Moon to make one revolution
What describes the "average speed" of a trip by car.
the distance traveled divided by how long it took
What is the photoelectric effect?
the emission of electrons from a clean metal surface when light shines on the surface
What is kinetic energy?
the energy an object has because of its motion
What is measured by the "newton?"
the force needed to accelerate a 1-kilogram mass at 1 meter per second per second
What is another simple way to describe the weight of an object?
the magnitude of the force attracting it toward Earth's surface
Your weight on a given planet could be calculated from which of the following?
the mass of that planet and its diameter
What else became calculable when Henry Cavendish calculated the value of G (the gravitational force between two objects on Earth)?
the mass of the Earth
When an object is hanging on the end of a vertical spring and oscillating up and down, what is frequency of the motion?
the number of cycles it travels in a unit of time
What is an antinode?
the position on a standing wave moving with the largest amplitude
The work that a force does by acting on an object is equal to what?
the product of force (in the direction of motion) and distance and is positive if the force and motion are in the same direction
What is the linear momentum of a moving object?
the product of its velocity and its mass
If the pole-vaulter were to land on concrete rather than on a cushion, the impulse that stops the fall would be what?
the same because impulse is the change in momentum of the object
When an object is hanging on the end of a vertical spring and oscillating up and down, which of these is a period?
the time the object takes to travel from the highest point to the lowest and back to the highest
What is the order of magnitude of a quantity?
the value of a quantity rounded to the nearest power of ten
Which unit is a unit of power?
the watt
When does kinetic friction occur in trying to push a heavy object?
when the force you apply is larger than the maximum static frictional force
A cyclist turns a corner with a radius of 44 m at a speed of 24 m/s. (a) What is the cyclist's acceleration? (b) If the cyclist and cycle have a combined mass of 90 kg, what is the force causing them to turn?
(a) a = v^2 / r a = 24^2 / 44 m a = 13.1 m/s^2 (b) F = m x a F = 90 kg x 13.1 m/s^2 F = 1180
A 41 kg person on a merry-go-round is traveling in a circle with a radius of 2 m at a speed of 3 m/s. (a) What acceleration does the person experience? (b) What is the net horizontal force? (c) How does it compare with the person's weight?
(a) a = v^2 / r a = 3^2 / 2 m a = 4.5 m/s^2 (b) F = m x a F = 41 kg x 4.5 m/s^2 F = 185 N (c) F = m x a W = m x g F/W = m x a/(m x g) = a/g = 4.5/10 = .45
Find the size of the net force produced by a 4 N and a 15 N force in each of the following arrangements. (a) The forces act in the same direction. (b) The forces act in opposite directions. (c) The forces act at right angles to each other.
(a) The forces act in the same direction. 4 + 15 = 19 N (b) The forces act in opposite directions. 15 - 4 = 11 N (c) The forces act at right angles to each other. F = sqrt(4^2 + 15^2) = sqrt(16 + 225) = sqrt(241) N 15.5 N
Which unit is a unit of acceleration?
(meters per second) per second
A very large magnetic field is 41 T. What is this field expressed in gauss?
1 T = 10000 G 41 T = 41000 G
A megaton is how many tons?
1 million
An observer traveling with the light clock in this figure reports that it takes 1 nanosecond (ns) for the light flash to go to the mirror and back. If the light clock is moving at 1/2 the speed of light relative to you, how long do you report for the light flash to go from the bulb to the mirror and back to the photocell? Note: 1 nanosecond = 10-9 second.
1.15 ns
The nucleus of a certain type of californium atom contains 98 protons and 153 neutrons. What is the total charge of the nucleus?
1.57e-17
A copper ion contains 29 protons, 30 neutrons, and 28 electrons. What is the net charge of the ion?
1.60e-19 C
This figure shows the force on a 0.1-kilogram mass at various distances from Earth. Notice that the force decreases as the square of the distance. Now, consider satellites A and B, both circling Earth. If A has ten times the mass of B but B is 1/10 of the distance to the center of Earth as is A, what is the gravitational force on A relative to that of B due to Earth?
1/10 the amount
Suppose the barn shown here is 10 meters long and the pole is 11.5 meters long. What is the minimum velocity that the pole has to travel relative to the barn for someone standing in the barn to measure the pole's length to be 10 meters or less?
1/2 of the speed of light
If a vibrating object has a frequency of 8 cycles per second, what is its period?
1/8 second
A kilometer is how many meters?
1000
If a hair dryer is rated at 1000 W, how much energy does it require in 6 minutes?
1000 watts means 1000 watts per hour so in 6 min it will take 1000/10 (60/6) or 100 watts.
What is the range from the size of protons and neutrons to the size of the visible universe?
10^41
At exactly noon, you pass mile marker 161 in your car. At 2:30 p.m. you pull into a rest stop at mile marker 320. What was your average speed during this time?
320 - 161 = 159 miles traveled / 2.5 hours traveling = 63.6 mph
You throw a ball straight up at 35 m/s. How many seconds elapse before it is traveling downward at 8 m/s?
35 m/s - (-8m/s) = 43 Rate of change of velocity = 10 m/s^2 Time = (change in velocity) / (rate of change of velocity) = (43 m/s) / (10 m/s^2) = 4.3 s
We can see light between what range of approximate wavelengths?
400 nanometers and 750 nanometers
What is the acceleration of a 1600 kg car if the net force on the car is 4600 N?
4600 N = 1600 kg x a a = 4600 N / 1600 kg a = 2.875 m/s
A 5 kg ball is thrown straight up in the air. What is the net force acting on the ball when it reaches its maximum height? What is the ball's acceleration at this point?
5 kg x 10 m/s^2 = 50 N acceleration is 10 m/s^2 because gravity suckuh
You observe that 30 crests of a water wave pass you each minute. If the wavelength is 10 m, what is the speed of the wave?
5 m/s
The electric potential energy of an object at point A is known to be 58 J. If it is released from rest at A, it gains 24 J of kinetic energy as it moves to point B. What is its potential energy at B?
58 - 24 = 34 J
If you are traveling at an average speed of 60 miles per hour, how long will it take to go from mile marker 1 to mile marker 7?
6 minutes
Approximate diameter of earth
6000 miles
What is the speed in meters per second of a baseball traveling at 67 mph given that 1 mph = 0.447 m/s?
67 x .447 = 29.949 m/s
Two 8 ohm resistors are connected in series to a 9 V battery. What single resistor, if connected to the battery alone (called the "equivalent resistance"), would draw this same current? What is the current through the battery?
8 x 2 = 16 ohms R = V / A A = V / R A = 9 / 16 A = .5625 amp
What are harmonic frequencies?
one more number times the fundamental frequency (i.e., fundamental frequency times two, times three, times four)
Which list includes only units of the U.S. customary system?
ounces, inches, and seconds
Why is acceleration a vector?
Acceleration is the rate of change of velocity, which is itself a vector.
How do velocity and acceleration differ?
Acceleration is the rate of change of velocity, while velocity is the rate of change of displacement.
What happens when a battery is recharged?
An electric charger runs current backward through the battery and reverses the chemical reactions.
Which of the following could happen if there were no air resistance and no gravity?
An object thrown at an angle upward would keep going up in the same direction for ever and never come down.
Why does the electric force dominate at the atomic scale while the gravitational force dominates on the large scale that includes the solar system and beyond?
Atomic particles have too little mass for gravitational attraction to compete with electric forces. At large distances, individual charges have essentially no effect since, overall, atoms are electrically neutral.
If bulb C were unscrewed, what would happen to the the brightness of bulb A and bulb B?
Bulb A and bulb B would be equally bright.
Which of these statements is true about a geosynchronous satellite?
It remains directly above a specific location on Earth's surface.
How can the electric field at a particular location from a collection of several different charges be calculated?
Calculate the field from each charge separately then add these contributions as vectors.
Which is true about comparing clocks in two different inertial systems?
Clocks in one system appear to run slower when viewed from the other.
A rock is dropped into an abandoned mine and a splash is heard 3 s later. Assuming that it takes a negligible time for the sound to travel up the mine shaft, determine the depth of the shaft and how fast the rock was falling when it hit the water.
Distance(s) = 1/2 x 10 m/s^2 x (3^2) s^2 = 45 m deep Velocity(v) = at = 10 m/s^2 x 3 s = 30 m/s
If we know the wavelength of a light beam, how can we calculate the corresponding frequency?
Divide the speed of light by the wavelength.
If f is the frequency of the emitted radiation, and h is Planck's constant (equal to 6.63 ✕ 10-23 J · s), the energy E each emitted quantum of energy has in Planck's explanation of blackbody radiation is:
E = h f
An X-ray photon has energy 1.40 x 10^15 J. What is its frequency?
E = h f f = E / h f = 1.40 x 10^15 J / 6.63 x 10^-23
Why do compasses point north?
Earth is a magnet with a magnetic south pole near the geographic North Pole.
Millikan's experiments on balancing charged oil droplets in an electric field first showed what?
Electric charges are integer multiples of a single fixed electron charge, which he measured.
Which is a key difference between electric charges and magnetic poles?
Electric charges can be separated while magnetic poles always occur together as opposite poles of equal strength.
What did Thomson discover about the electron that changed a long-accepted idea about atoms?
Electrons are smaller than atoms.
Which of these was NOT a difficulty initially met in explaining the photoelectric effect?
Electrons could not escape from solid materials.
In this figure, why is the kinetic energy gained by the falling ball equal to the change of potential energy? (Assuming no loss of energy due to friction.)
Energy conservation requires that the total energy remains constant. In this example, the total energy is either in the form of kinetic energy or potential energy.
Which of these is a result first obtained by Planck?
Energy is emitted in discrete quanta.
What is the electric field at a distance of 1 cm from 2 mC of negative charge?
F = (k)(q1)(q2)/(r^2) F = E(q) E = (k)(q)/(r^2) k = 9*10^9 q = 2*10^-3 => convert millicoulombs to coulombs, 1 mC = 0.001 C r = 0.01 => convert cm to m, 1 cm = 0.01 m E = (9*10^9) (2*10^-3)/(0.06)^2 = 1.80 x 10^11
The gravitational force between two very large metal spheres in outer space is 40 N. How large would this force be if the mass of each sphere were doubled?
F = Gcm1m2 / r^2 where G is the gravitational constant, M and m are the masses and r is the distance of separation. Doubling both masses quadruples the force. F = 160 N
A solid lead sphere of radius 10 m (about 66 feet across!) has a mass of about 57 million kg. If two of these spheres are floating right next to each other (centers 20 m apart) in deep space, the gravitational attraction between the spheres is only 540 N (about 100 pounds). How large would this gravitational force be if the distance between the centers of the two spheres were doubled?
F = Gcm1m2 / r^2 Gc = 6.6726 x 10^-11 N-m2/kg2 F = [(6.6726 x 10^-11)(57,000,000kg)(57,000,000kg)] / 20m^2 This is how you got roughly 540N So plug all your numbers in again, except change the r value to 40m^2 F = [(6.6726 x 10^-11)(57,000,000kg)(57,000,000kg)] / 40m^2 F = 135 N
Two spacecraft in outer space attract each other with a force of 5 N. What would the attractive force be if they were one-half as far apart?
F = Gcm1m2 / r^2 Gc = 6.6726 x 10^-11 N-m2/kg2 The force is inversely proportional to the square of the distance, so it would quadruple. The answer is 20 N.
If a space explorer with a mass of 71 kg has a weight of 430 N on a newly discovered planet, what is the acceleration due to gravity on this planet?
F = m x a 430 N = 71 kg x a a = 430 N / 71 kg = ~6 m/s^2
A fully equipped astronaut has a mass of 180 kg. If the astronaut has a weight of 675 N standing on the surface of a planet, what is the acceleration due to gravity on this planet?
F = m x a 675 N = 180 kg x a a = 675 N / 180 kg = 3.75 m/s^2
A crate has a mass of 19 kg. What applied force is required to produce an acceleration of 3 m/s2 if the frictional force is known to be 98 N?
F = m x a F = (applied force - friction) = x - 98 N m = 19 kg a = 3 m/s^2 F = 57 N 57 N = x - 98 N 155 N = applied force
If a sled with a mass of 34 kg is to accelerate at 3 m/s2, what net force is needed?
F = m x a F = 34 kg x 3 m/s^2 = 102 N
A 5 kg ball has been thrown vertically upward. If we ignore the air resistance, what are the direction and size of the net force acting on the ball while it is traveling upward?
F = m x a F = 5 kg x 10 m/s^2 = 50 N downward
What net force is needed to accelerate a 70 kg ice skater at 2 m/s2?
F = m x a F = 70 kg x 2 m/s^2 = 140 N
By what distance must two charges of +2 C and +2 C be separated so that the repulsive force between them is 3.70 x 10^10 N?
F = q1*q2/(4*π*ε0*d²) Easy
What is the electric force of attraction between charges of 3 C and -2 C separated by a distance of 1 m?
F = q1*q2/(4*π*ε0*d²) q1 = 3 C q2 = -2 C d = 1 m ε0 = 8.85*10^-12 F/m F = 5.4 x 10^10 N
A rope is used to pull a 8 kg block across the floor with an acceleration of 3 m/s2. If the frictional force acting on the block is 44 N, what is the tension in the rope?
F(net) = m x a Ft - Ff Ft = (m x a) + Ff Ft = (8 kg x 3 m/s^2) + 44 N Ft = 68 N
Why does the bulb light when connected as in the figure at the right, but not in the situation shown in the figure at the left?
For electric current to flow continuously through the bulb, there must be a connection between the positive and the negative terminals of the battery.
A spring gun fires a ball horizontally at 15 m/s. It is mounted on a flatcar moving in a straight line at 22 m/s. (a) Relative to the ground, what is the horizontal speed of the ball when the gun is aimed forward? (b) Relative to the ground, what is the horizontal speed of the ball when the gun is aimed backward?
Given that the speed of the ball is Uball = 15 m/s The velocity of the car is Ucar = 22 m/s (a) Relative to the ground, the horizontal speed of the ball when the gun is aimed forward V = Uball +Ucar =15 + 22 = 37m/s (b) Relative to the ground, the horizontal speed of the ball when the gun is aimed backward V = Ucar- Uball = 22 - 15 = 7 m/s
A woman with a mass of 65 kg climbs a set of stairs that are h = 6 m high. How much gravitational potential energy does she gain?
Gravitational PE = mgh m = 65 kg g = 10 m/s^2 Change in height = 6 m She gains (65 kg) x (10 m/s^s) x (6 m) = 3900 J
Which was one of the basic principles from which Newton derived the law of gravity?
Heavenly motions should follow the same rules as motions on earth.
If a mass on a spring has a frequency of 19 Hz, what is its period?
Hz = period per second 1 / 19 = .0526
For sound waves, which travel at 343 m/s in air at room temperature, what frequency corresponds to a wavelength of 0.90 m?
Hz = period per second 343 meters / second x 1 period / .9 meters = 381 Hz
If the breakers at a beach are separated by 6.0 m and hit shore with a frequency of 0.32 Hz, with what speed are they traveling?
Hz = period per second 6 m / period x .32 periods / second = 1.92 m/s
Which is the correct expression for current I in terms of the charge Dq and the time Dt it takes the charge to pass a particular location in the wire?
I = Dq / D t
Which of these is an accurate statement of Newton's first law?
In the absence of an unbalanced force, the velocity of an object remains constant.
A 0.5 kg air-hockey puck is initially at rest. What will its kinetic energy be after a net force of 0.3 N acts on it for a distance of 1.1 m?
Initial kinetic energy Ki = 0 (because the puck is at rest) Work done W = force*distance = 0.3 x 1.1 = 0.33 J Final kinetic energy Kf = ? Kf - Ki = W Kf - 0 = 0.33 J Kf = 0.33 J Ans: 0.33 J
What is the behavior of Foucault's pendulum?
It changes the direction of its back and forth swing because Earth rotates beneath it.
When an item has been launched into orbit, what happens?
It continues to fall but its path never reaches the ground.
What happens to the charge that leaves a battery in a complete circuit that includes a light bulb?
It goes through the light bulb and returns to the other end of the battery.
Which is always true of an uncharged object?
It has equal amounts of positive and negative charge.
What do we know about the direction of momentum?
It has the same direction as the object's velocity.
Which of these is true about the absolute temperature of an ideal gas?
It is directly proportional to the average kinetic energy of the gas particles.
Which of the following is true of the kinetic energy of an object?
It is directly proportional to the square of its speed.
What is electric potential energy?
It is the work done in bringing the object from some reference location to the object's location.
What is the electric potential at a given point in space, in terms of the work done to bring a small positive test charge from a reference location where the potential is taken to be zero?
It is the work done to bring the test charge to the point, divided by its charge, expressed in volts.
What is the charge on a single electron or proton?
roughly 10-19 coulomb
You reach out the second story window, which is 5 m above the sidewalk, and throw a 0.1 kg ball straight upward with 6 J of kinetic energy. (a) What is the ball's gravitational potential energy when it is released? (b) What is the ball's gravitational potential energy just before hitting the sidewalk? (c) What is the ball's kinetic energy just before hitting the sidewalk? (d) How would the answer to part c change if the ball had initially been thrown straight down with 6 J of kinetic energy?
KE = (½) • m • V² PE = mgh (a) PE = (.1)(10)(5) PE = 5 J at t = 0 (b) PE = (.1)(10)(0) PE = 0 (c) KE = 6 J PE = 5 J KE = 6 + 5 = 11J (d) stay the same
Which of these is the kinetic energy of a particle of mass m moving at speed v?
KE = 1/2 mv2
A 3 kg toy car with a speed of 8 m/s collides head-on with a 2 kg car traveling in the opposite direction with a speed of 1 m/s. If the cars are locked together after the collision with a speed of 4.40 m/s, how much kinetic energy is lost?
KE = 1/2 mv^2, = 1/2 (3 x (8^2)) = 96 Joules. Same again, 1/2 (2x(1^2)) = 1 Joule. Total KE = 97 Joules. (2 + 3) = 5kg. KE = 1/2 (5 x (4.4^2)) = 48.4 Joules. Loss = (97 - 48.4) = 48.6 Joules.
What is the kinetic energy of a 1200 kg sports car traveling down the road with a speed of 30 m/s?
KE=1/2 x mv^2. v = 30 m = 1200 KE = 5.40 x 10^5
What, according to the modern view, was the reason Michelson's and Morley's experiment failed to observe motion relative the ether?
Light does not require a medium to travel through.
Which of these statements is correct?
Like charges repel each other; unlike charges attract each other.
Which of these statements about the poles of magnets is correct?
Like poles repel; unlike poles attract.
What is one thing that electrical engineers do to minimize power loss between the plant and your home?
Lower the resistance between the two as much as possible.
Which of the following statements is currently believed to be true?
Magnetism is caused by electric current loops at the atomic level.
Which of the following statements is true about any collision between two objects with no net applied force acting?
Momentum is always conserved and kinetic energy is sometimes conserved.
What makes a reference system "inertial"?
Newton's first law applies in that system.
If objects on the Moon weigh 1/6 the amount they weigh on Earth, what should one conclude about the mass of objects on the Moon?
Nothing. The mass of objects are the same everywhere.
The astronaut's experiment with the hammer and the feather illustrates what?
Objects of different size, shape, and mass fall at the same rate in a vacuum.
What is the power rating of a heating coil with a resistance of 14 ohm that draws a current of 24 A?
P = I^2 x R P = 8060 W
If a clock draws a maximum current of 2 mA from a 110 volt line, what is its maximum power consumption?
P = V x A P = 110 x .002 = .22 W
If a 67 kg sprinter can accelerate from a standing start to a speed of 10 m/s in 3 s, what average power is generated?
P = W / t = ΔKE / t = (1/2)mv^2 / t P = (1/2)(67)(100) / 3 = 1120 W
If a 0.2 kg ball is dropped from a height of 5 m, what is its kinetic energy when it hits the ground?
PE = mgh PE = (.2)(10)(5) KE = PE KE = 10 J
What is the force on a proton located in an electric field of 3500 N/C?
Proton charge = 1.602×10−19 Coulombs 1.602×10−19 x 3500 F = 5.607 x 10^-16 What is the proton's acceleration? F = m x a a = F / m m for proton = 1.6726219 × 10-27 kg a = 3.35e+11
What is the resistance of the coil in a 1700 W heater? (Assume that the heater is connected to a 120 V source.)
R = E^2 / P R = 8.47
You plug a vacuum cleaner into a 110 volt outlet with nothing else on the circuit. If the 25 ampere circuit breaker is tripped, what is the maximum possible resistance of the vacuum's motor?
R = V / A 110 / 25 = 4.4
A 4 ohm and a 4 ohm resistor are connected in series to a 12 V battery. What is the current through each resistor?
R = V / A 4 = 12 / A 12 / 4 = A A = 1.5
What is the resistance of a lightbulb that draws 0.6 A when it is plugged into a 110 V outlet?
R = V / I V = voltage & A = Amp R = 110 / .6 = 183 ohms
If you began at rest and ended at rest, and the average speed of your trip was 10 kph, which is true?
Sometimes you were going faster than 10 kph.
Which statement about terminal speed is true?
Terminal speed is affected by size, weight, and shape.
According to Newton's theory of gravity, why does the Moon have a much lower acceleration than a falling object on Earth?
The Moon is farther away from Earth's center than the object falling at Earth's surface.
What happens inside a reference system with a constant acceleration?
The acceleration can be recognized because a falling object seems to move away from the direction of acceleration instead of straight down.
If you are whirling a ball on a string and you suddenly cut the string, what happens?
The ball goes off in a straight line based on where it was heading when the string was cut.
Why couldn't Newton determine the value of the gravitational constant?
The constant was too small to measure with existing instruments
An electric field produces a magnetic field even when there is no wire to conduct a current provided which of the following is also true?
The electric field is changing as time passes.
In this photo, water drops produce disturbances that move outward in circular patterns. What moves outward as drops hit the water's surface? (Hint: If a cork were floating on the water's surface, what would be its motion?)
The energy of neighboring water molecules.
What happens to centripetal force when speed decreases, in the special case that the object continues moving in a circle of the same radius?
The force also decreases.
How does the force between two otherwise unchanged electrical charges vary with distance?
The force decreases by the square of the distance.
In part (a) of this figure, three identical, equally spaced objects are dropped. In part (b), the two green blocks are moved closer together before they are dropped. In part (c), the two green blocks are combined to form one larger block. Contrasting Galileo's and Aristotle's views, what is the most plausible statement about the speed of the large green block compared with that of the small red block?
The green block can be seen as two side-by-side smaller blocks falling at the same rate, hence the larger and smaller blocks fall at the same rate.
A radio-controlled car increases its kinetic energy from 2 J to 10 J over a distance of 5 m. What was the average net force on the car during this interval?
The increase of kinetic energy is equal to the Work. ΔE = W = F x s F = W / s F = (10-2) / 5 = 1.6 N
Which has greater momentum in this photo: the non-moving ship or the kayak moving at the slow speed of 1 meter in ten seconds?
The kayak because it has non-zero momentum while the ship at rest must have zero momentum.
In a rollercoaster, provided losses of thermal energy because of friction can be neglected, which of the following is true?
The kinetic energy decreases as the car moves to the top of the slope.
Which of these is the Galilean principle of relativity?
The laws of motion are the same in all inertial reference systems.
The first postulate of special relativity says what?
The laws of physics are the same in all inertial reference systems.
In these figures, we see a boy named Billy riding a carnival ride called the Rotor and the free-body diagram for the forces acting on him. What must be the magnitudes of the vectors f(wall,Billy) and W(Earth,Billy) if Billy remains at the same height along the wall?
The magnitudes of f(wall,Billy) and W(Earth,Billy) are equal.
If the momentum of one object changes in a system that is subject to no net external force, what else must happen?
The momenta of the other objects in that system change to cancel out the first change.
A compass needle is a magnet with a north and south pole. If a tiny compass were placed in the magnetic field shown in the figure, how would the compass needle be aligned in the magnetic field?
The needle would line up with a magnetic field line with the compass needle pointing in the same direction as the arrows in the diagram.
If two identical balls have momenta that are equal in magnitude but opposite in direction, what do we know about the speeds of the two balls after the two collide?
The speeds of the two balls will always be the same.
Which of these statements is true about the statement that the value of G is the same throughout the universe?
The statement is believed to be true because it has never been disproved.
When you walk forward on a scooter that was previously at rest, how do you calculate the total momentum of you and the scooter?
You don't have to calculate it; you already know that it is zero.
What does the law of conservation of momentum tell us about collisions?
The total momentum in the system does not change because of a collision.
If you are traveling at close to the speed of light, on your way back to Earth from a distant star. In your own reference system of the space ship, compared with the reference system of Earth,
The travel time to Earth is shorter and the distance to Earth is shorter.
If you hear a tree fall, what do you know?
The tree hitting the ground was an inelastic collision.
Why don't the two forces in Newton's third law cancel each other?
They act on two different objects.
Which of the following is true about frictional forces?
They can decrease kinetic energy.
What made Maxwell's equations conflict with Galilean invariance while Newton's laws did not conflict?
They depended on velocity rather than acceleration.
If electric field lines flow out of a positive charge, as shown in this figure, where do these same lines terminate?
They terminate on negative charge, not shown in the figure.
What is the acceleration due to gravity at a distance of one Earth radius above the Earth's surface?
This is 2 R from the Earth's centre of mass. g depends on 1/R^2, so at this height must be 1/2^2 less than at a distance R The g you want is 10 / 4 = 2.5 m/s^2
If kinetic energy is conserved by the apparatus (newtons cradle) shown in this figure, why do we find in class demonstrations that the balls eventually come to rest?
Total energy, not kinetic energy, is conserved, the rest of the energy going to heat; but the heat loss in this experiment is normally ignored since it occurs very slowly.
If the person shown here on the ground is in an inertial reference system, his friends in the van moving by at constant velocity are also in an inertial reference system.
True
This graph shows the adjustment factor versus the ratio of the speed of the system or object to the speed of light. The graph implies that, if travel at speed c were possible, a clock traveling at the speed of light would stop.
True
What is the correct method to subtract a vector from another vector?
Turn the arrow you are subtracting around, and then add.
Points A and B each have an electric potential of +2 V. How much work is required to take 10 mC of charge from A to B?
V = W / Q W = V x Q = 2 x 10 = 20
How are speed and velocity related?
Velocity specifies both the speed and the direction of a moving object.
A tennis ball is hit with a vertical speed of 15 m/s and a horizontal speed of 40 m/s. How long will the ball remain in the air? How far will it travel horizontally during this time?
Vertical speed Vy = 15 - gt At max height Vy = 0 => t = 15/g Same time until hits the ground 2t = 30 / g = 30 / 10 m/s^2 = 3 s It will travel 120 meters because 3 seconds in the air x 40 m/s is 120 meters
The demonstration in this figure is often shown as a magician's trick. What in fact is the "trick?"
When the magician yanks the tablecloth rapidly, the inertia of the dishes prevents them from accelerating significantly during the short time the force of friction from the moving tablecloth acts.
Which of the following is true about simultaneous events?
Whether two events are simultaneous depends on the reference system the events are viewed from.
In this figure, if there were twice as much charge on the object on the right, would the forces still be equal and opposite?
Yes, but the magnitudes of the forces will be twice as large.
What does Newton's second law relate?
net force, mass, and acceleration
A 30-06 bullet has a mass of 0.010 kg. If the average force on the bullet is 9300 N, what is the bullet's average acceleration?
a = F / m a = 9300 N / .01 kg = 930000 = 9.3 x 10^5
What is electric current?
a continuous flow of charge
What is centripetal force?
a force that seeks the center of a circle
What is a short circuit?
a path with a very low resistance
What is an inverse-square relationship between force and distance?
a relationship where the increasing the distance by a factor decreases the force by dividing it by the square of that same factor
According to the Aristotelian view of motion, which of these would NOT work?
a rocket ship going to the moon because he believed motion requires force
Ignoring air resistance, which of these is the acceleration of a falling object?
about 10 (meters per second) per second
A ball thrown vertically upward, at the top of its path (just before it starts to fall) has which of the following?
an instantaneous speed of zero
How small a time interval is needed for a good calculation of instantaneous speed?
an interval short enough so that the answer won't change very much if you use a shorter one
Where does diffraction take place?
around the edges of barriers
Why is Earth a non inertial reference system?
because of all the various ways it moves, including rotation, revolution, and the movement of the Galaxy
Aristotle believed that the speed at which objects fall
depends on both their weight and the medium they fall through (and he was partly right).
What is the force on the magnet that results from the motion shown in this figure (going down)?
directly upward
A collision in which kinetic energy is conserved is called what?
elastic
What atomic interactions create resistance?
electrons slowing down as they bump into other atoms
List these in order of smallest to largest centi, femto, mega, nano, tera
femto, nano, centi, mega, tera
Which of these would be represented by a vector?
fifteen feet north
Which of the following is Newton's second law of motion in the form of an equation?
force = mass x acceleration
What changed Newton's original work on the movement of the Moon around the Earth into the law of universal gravitation?
his conclusion that the same laws applied to all objects, no matter how small
Newton's laws work in accelerated reference systems if
inertial forces are included.
What is the unit for kinetic energy?
joule
Momentum is measured in what unit?
kilogram-meters per second
Which list includes only units of the metric system?
kilograms, micrometers, and milliseconds
What are wavelengths of light are most efficiently measured in?
nanometers
A ground-based observer measures a rocket ship to have a length of 170 m. If the rocket was traveling at 67% of the speed of light when the measurement was made, what length would the rocket have if brought to rest?
y = 1 / sqrt(1 - (v / c)^2) y = 1 / sqrt(1 - (.67c / c)^2
Low-pressure sodium lights produce light that consists only of the colors in the emission spectra of sodium. From the emission spectra in this figure, what is the color of low-pressure sodium light?
yellow
When the pendulum bob shown here is at its highest point, its velocity is ________ and its acceleration is___________.
zero/a maximum
