PHY 102 Final Exam

Which scientist discovered that the universe is made up of galaxies? Correct answer- Hubble One half second after starting from rest, a freely falling object will have a speed of about Correct answer- a = Vf-Fi / t , 9.8m/s^2 = Vf - 0 / .5s, Vf = 4.9 m/s Which part of the sun is the outermost layer? Correct answer- Corona The slope of a velocity vs time graph tells you the Correct answer- acceleration True or False: The universe is expanding. Correct answer- True Stars that have ___ mass than the sun will end their lives as brown dwarfs. Correct answer- Less Which part of the sun i considered the apparent surface of the sun? Correct answer- Photosphere Acceleration is the measure of the change in what? Correct answer- Velocity Which of the following is a private research lab? Correct answer- Carnegie Institution Which of the following is Kepler's first law? Correct answer- Planets move in elliptical orbits with the sun at one focus Which of the following is not part of the scientific method? Correct answer- Belief In the SI unit system, mass is measured in units of Correct answer- Kilograms True or False: Velocity has a direction Correct answer- True True or False: Stars that are moving away from us are called "red-shifted". Correct answer- True In each second of a fall, the distance a freely falling object will fall is Correct answer- Increasing The language of physics is Correct answer- Mathematics Approximately how old is the universe? Correct answer- 15 billion years If a car increases its velocity from zero to 60 km/h in 6 seconds, its acceleration in m/s/s is Correct answer- 60km | 1000m | 1 hr | 1 min 1 hr | 1 km | 60 min | 60 s = 16.67 m/s a = 16.67 - 0 / 6 = 2.8 m/s/s Which astronomer was the first to put the sun at the center of the universe? Correct answer- Copernicus True or False: Stars do not shine during the day Correct answer- False Which astronomer is credited with being the first to explain the complex motion of the stars and planets? Correct answer- Ptolemy An educated guess is a Correct answer- hypothesis If a car accelerates form rest at 10 meters per second per second, its speed (in m/s) 3 seconds later will be about Correct answer- 10 m/s^2 = Vf-0 / 3s Vf = 30 m/s In the SI unit system, time is measured in units of Correct answer- seconds If an object falling freely were somehow equipped with an odometer to measure the distance it travels, then the amount of distance it travels each succeeding second would be Correct answer- greater than the second before Which astronomer spent 25 years making measurements of the stars' and planets' positions, only to die before the data was analyzed? Correct answer- Brahe In which part of the sun does most fusion take place? Correct answer- Core In SI units of acceleration are Correct answer- m/s/s True or False: Telescopes are often placed on mountains because there is less atmosphere at high elevations. Correct answer- True Which of the following is Kepler's second law? Correct answer- A line from the sun to the earth sweeps out equal areas in equal times Which an object near the Earth's surface is in free fall, its Correct answer- velocity increases Which of the following is a government research lab? Correct answer- Argonne National Lab Which element is most abundant in stars? Correct answer- Hydrogen Approximately how many years remain in the life of the sun? Correct answer- 5 billion Which of the following can only be seen during a solar eclipse? Correct answer- Corona and Chromosphere Stars that have ___ mass than the sun will end their lives as neutron stars. Correct answer- More True or False: One of the Keck telescopes is a reflecting telescope. Correct answer- True A ball is thrown straight upward into the air. Neglect air resistance. While the ball is in the air, its acceleration Correct answer- remains constant The SI units of velocity are Correct answer- m/s The net force on a moving object suddenly becomes zero. The object then Correct answer- continues at a constant velocity A gun with a muzzle velocity of 93 m/s is fired horizontally from a tower. Neglecting air resistance, how far downrange in meters will the bullet be 8.3 seconds later? Correct answer- V = d/t 93 m/s = d/ 8.3s d = 771.9 A ball is moving at 78 m/s and has a momentum of 50 kg m/s. What is the ball's mass in kg? Correct answer- P =mv 50 kgm/s = m(78 m/s) 0.64 A force accelerates an object of mass M. The same force applied to a second object produces 4 times the acceleration. What is the mass of the second object? Correct answer- F = ma M/4 The SI units of work are Correct answer- Joules A 23 kg woman riding a bicycle has a speed of 3.5 m/s at the bottom of the hill. As she travels up the hill, she does not pedal, and gradually coasts to a stop. How far in meters (vertically) above the bottom of the hill is she when she stops? Correct answer- KE = 1/2 mv ^2 at bottom 1/2(23 kg)(3.5 m/s)^2 = 140.9 J PE = mgh at top 140.9 J = (23 kg)(9.8 m/s) 0.63 A projectile is fired horizontally in a region of no air resistance. The projectile maintains its horizontal component of velocity because Correct answer- it is not acted on by any horizontal forces True or False: A grasshopper leaps into the air at a 62 degree angle above the horizontal. At its highest point, the grasshopper's velocity and acceleration are equal to zero. Correct answer- False Roll a bowling ball off the edge of a table. As it falls, its horizontal component of velocity Correct answer- remains constant A 50 kg sack is lifted 2 meters from the ground and a 25 kg sack is lifted 4 meters from the ground in the same amount of time. The power expending in raising the 50 kg sack is Correct answer- P = W /t the same If you apply the same force to objects with masses M and 4M, the acceleration of mass M is Correct answer- F = ma four times the acceleration of mass 4M The power required to exert 1 N force, over a distance of 1 m in 1 second is Correct answer- P = W/t W= Fd P = 1N * 1m / 1S 0.8 Energy in motion is ___ energy. Correct answer- Kinetic A bullet fired horizontally over level ground hits the ground in 0.5 seconds. If it had been fired with twice the speed in the same direction, it would have hit the ground in Correct answer- 0.5s A woman runs up a flight of stars. The gain in her gravitational potential energy is 100 J. If she runs up the same stairs with twice the speed, what is her gain in potential energy? Correct answer- 100 J Using 1000 j of work, a toy elevator is raised from the ground floor to the second floor in 20 seconds. The power needed to do this job was Correct answer- P = w/t P = 1000 J / 20 s 50 W Padded dashboards in cars are safer in an accident than non-padded ones because an occupant hitting the dash has Correct answer- increased time of impact An object moves with decreasing speed. Which of the following is true? Correct answer- The work done on the body is negative, and the kinetic energy is decreasing Which of the following statements is Newton's 3rd law? Correct answer- For every action there is an equal and opposite reaction An elevator lifts a person from the 1st floor to the 4th floor in 3.7 seconds. If the power output of the elevator is 46 W, what is the work done by the elevator in J? Correct answer- P = W/t 46 W = w/3.7 seconds 170.2 A hockey puck is set in motion across a frozen pond. If friction and air resistance are neglected, the force required to keep the puck sliding at constant velocity is Correct answer- zero A gun with a muzzle velocity of 22 m/s is fired horizontally from a tower. Neglecting air resistance, how far downrange in meters will the bullet be in 1 second later? Correct answer- V = d/t 22 m/s = d/1s 22 If an object is raised twice as high, its potential energy will be Correct answer- PE = mgh twice as much Two objects have the same size and shape, but one is much heavier than the other. When they are dropped simultaneously from a tower, they reach the ground at the same time, but the heavier one has a greater Correct answer- Momentum A 3 kg mass at the Earth's surface weighs ___ N. Correct answer- W = mg W = 3 kg * 9.8 m/s/s 29.4 A ball rolling down an incline has its maximum kinetic energy at Correct answer- the bottom Susan ascends a mountain via a short, steep trail. Sean ascends the same mountain via a long, gentle trail. Which of the following statements is true? Correct answer- Susan gains the same gravitational potential energy as Sean. An object that has kinetic energy must be Correct answer- moving A 910 kg car moving at 5 m/s brakes to a stop in 5 seconds. The magnitude of the average braking force in N is Correct answer- F = change in momentum / t; P = mv F = 0 - (910 kg)(5 m/s) / 5 seconds 910 The energy stored in one pound of fat is Correct answer- 3500 Cal A hunter on level ground fires a bullet at an angle of 2 degrees below the horizontal while simultaneously dropping another bullet from the level of the rifle. Which bullet hit the ground first? Correct answer- The fired one If you push an object twice as far while applying the same force, you do Correct answer- W =Fd twice as much work If you push for half hour or a whole hour against a stationary wall Correct answer- no work on the wall is done in either case A 2.5 kg car accelerates at a rate of 5 m/s/s over a distance of 57 m. What is the work done in Joules to accelerate the car? Correct answer- F = ma; 2.5 kg * 5 m/s/s = 12.5 N W = Fd; 12.5 N * 57 m 712.5 If an object's speed is doubled, its kinetic energy is Correct answer- quadrupled An object lifted 10 meters gains 200 J of potential energy. if the same object is lifted 20 meters, its potential energy is Correct answer- twice as much A 75 kg man climbs the stairs to the fifth floor of a building, a total height of 16 m. His potential energy has increased by approximately how many Joules? Correct answer- PE = mgh 75 kg * 9.8 m/s/s * 16 m 11760 A straight bar magnet is initially 4 cm long, with the north pole on the right and the south pole on the left. If you cut the magnet in half, the right half will Correct answer- still contain a north pole on the right and a new south pole on the left The input current of a transformer is 4 A. The primary coil has 50 loops and the secondary has 25 loops. The current that the transformer puts out is Correct answer- (Primary loops / Secondary loops) * input current 50 / 25 = 2 * 4 = 8 A 8 A Entropy is closely related to the Correct answer- 2nd law of thermodynamics A transformer has 83 loops in the primary coil and 61 loops in the secondary coil. If the input current is 6.1 A, what is the output of the transformer in Amps? Correct answer- (Primary loops / Secondary loops) * input current 83 / 61 = 1.36 * 6.1 8.3 The molecules in an object with a higher temperature Correct answer- move faster As a system becomes more disordered, entropy Correct answer- increases A 3.6 Ohm resistor has a 5 A current in it. What is the voltage across the resistor in Volts? Correct answer- V = IR V = 5 * 3.6 18 True or False: Temperature is a form of energy Correct answer- False A temperature difference of 10 degrees Celsius is also equal to a temperature difference of 10 on the Correct answer- Kelvin scale The power dissipated in a 7.7 ohm resistor carrying 3 A is Correct answer- P = RI^2 P = (7.7 ohm)(3 A)^2 69.3 An electric motor is most similar to Correct answer- an electric generator The direction of an electric field is the direction of the force that the field would exert on Correct answer- a positive charge A device that transforms electrical energy to mechanical energy is a Correct answer- motor The power dissipated in each of two light bulbs is the same. The voltage across light bulb A is twice that of light bulb B. If the resistance of light bulb b is R, what is the resistance of light bulb A? Correct answer- 4R Charges in Q1 and Q2 exert repulsive forces of 4.1 N on each other. What is the repulsive force in Newtons when their separation is decreased so that their final separation is 72% of their initial separation? Correct answer- 5 Systems that are left alone, tend to move toward a state of Correct answer- more entropy Your feet feel warmer on a rug than on a tile floor because a rug Correct answer- is a better insulator than tile A power line with a resistance of 7.1 ohms has a current of 85 A in it. The power dissipated in the line is Correct answer- P = RI^2 P = (7.1 ohms)(85 A)^2 51297.5 Two charged particles held close to each other are released. As they move, the force on each particle increases. Therefore, the particles must have Correct answer- opposite signs Two charged particles repel each other with a force F. If the charge of one of the particles is doubled and the distance between them is also doubled, then the force will be Correct answer- F/2 The electrical force between charges is strongest when the charges are Correct answer- close together The same voltage is measured across two wires. Wire A carries twice the current of wire B. If the resistance of of Wire B is R, what is the resistance of wire A? Correct answer- V = IR = R/2 True or False: Heat is a form of energy. Correct answer- True A current of 3.6 passes through a lamp with a resistance of 7.1 ohms. What is the power supplied to the lamp in Watts? Correct answer- P = RI^2 P = (7.1 ohms)(3.6 A)^2 92.01 Two protons attract each other gravitationally and repel each other electrically. By far the greater force is Correct answer- the electrical repulsion A positive ion has more Correct answer- protons than electrons The freezing point of water in the Fahrenheit scale is Correct answer- 32 degrees F The specific heat capacity is the heat required to raise ___ of a substance by ___. Correct answer- 1 gram, 1 degree C A main difference between gravitational and electric forces is that electric forces Correct