Regents Physics June 2007 Exam Explained Anna Hinchcliffe

Regents Physics June 2007 Exam Explained Anna Hinchcliffe

Part A- #1 • A vector is something that is measured in magnitude and • So, if you move a distance of 3 direction meters north and 4 meters east, you have a total displacement • A scalar is something measured (vector) of 5 meters only in magnitude • So 5 m/s is speed (scalar), while 5 m/s east is velocity (vector) • Another example is distance vs. displacement

Part A #1 • Magnetic field strength at a given point has a certain strength and • Therefore, the only choice that is direction, making it a vector not a vector is #1, electric charge • Electric charge is a scalar because it only has magnitude, for example a charge of 3 coulombs • Electric charge has no direction associated with its magnitude

Part A #2 • We have the distance (6 m), and the time (2. 7 s) • We also have the initial velocity (0 m/s) • the unknown is acceleration • The formula for that best fits these variables is:

Part A- #2 • After you solve for the unknown, you then plug in all your numbers and solve the equation • So, the answer is #1, 1. 6 m/s 2

Part A-#3 • We have the mass (2 kg), the weight (19. 6 N) and the • So the mass would still be 2 kg, so acceleration due to gravity on the answer is #2 2) Mars (3. 71 m/s • But the question is asking what the mass is on Mars compared to the mass on Earth • The mass of an object stays constant no matter what planet it’s on, while the weight changes

Part A-#4 • When an object is moving in a circle, the acceleration is constantly changing • The velocity is pointed in tangent • The acceleration is pointed to the circle toward the center too • And the centripetal force is pointed towards the center of the • So in the problem, the acceleration is pointed towards circle the east, #4

Part A #5 • Two concurrent forces are two forces acting at the same time on an object at the same point • To reach equilibrium, the net force (total of all force acting on an object) needs to equal zero • As the angle between 2 concurrent forces decreases, the resultant force increases • So, since the resultant force increases, it would take a larger force in the opposite direction to reach equilibrium • The answer is #2, increases

Part A #6 • Displacement is the scalar quantity of the change in an objects position • So, if a kid walks 5 meters north, 4 meters east, the 2 meters south • The kid ends up 4 m east and 3 m north from the start • Using Pythagorean theorem you find the total displacement is 5 m • So the answer is #2, 5 m

Part A #7 • We know that x, the change in position of the spring is 0. 075 meters, and the force acting on the spring is 5 Newtons • The equation for the spring constant ‘k’ is • By solving the equation we see the answer is #2, 67 N/m

Part A #8 • We have he mass (0. 5 kg), the radius (0. 25 m), and velocity (4 m/s) • The unknown is the acceleration of the circular path • The equation for centripetal • After solving the equation we see acceleration is : that the answer is #4, 64 m/s

Part A #9 • For this problem, we know the • Momentum can also be measured mass of the cart is 1 kg by the force times time, or p=Ft • We also know momentum(p) is measure by the equation p=mΔv • So by measuring each option we’ll find out which has the most • By solving these equations momentum we see that #3 has the most momentum of 10 N/s

Part A #10 • We know that the moons mass is force, they exert on each other is m, we also know the earths mass equal is 81 m and the gravitational force • So, the answer is still F, #1 the earth exerts on the moon is F • The unknown is the gravitational force the moon exerts on the earth • Because there is no change in the mass or distance between these two objects the gravitational

Part A #11 • The known variables we are given are mass and speed • Kinetic energy is measured by the equation of KE=1/2 mv 2 • So if we figure out what each objects KE is we can figure out which two are equal • By solving the equations we find Band C are equal, so choice #4 is the answer

Part A #12 • The given variables are force (5 N), • After solving the equations, we see the answer is #3, or 30 J mass (3 kg), and distance (6 m) • The unknown is the kinetic energy • The kinetic energy plus the potential energy is equal to the total energy • The total energy is equal to Force times distance

Part A #13 •

Part A #14 •

Part A #15 •

Part A #16 •

Part A #17 • We know the first wire has a resistance (R), length (L), and cross-sectional area (A). • We also know since both wires are copper, they have the same resistivity (p) • The formula for resistance is • So to find the resistance of the second wire we can plug in the values of 2 L and 1/2 A to the equation • By doing his we find the answer is #4, 4 R

Part A #18 • In a circuit, we know that voltmeters must be in series with the lamp, and if the switch is open, the lamp won’t operate correctly • So we know that #1 and #2 are not correct, and #3 isn’t either, because they are all parallel circuits • So the answer is #4

Part A #19 • To better understand this, we can • The formula for this is draw out the circuit, which is • After we solve for the unknown, parallel we plug in the numbers • Since each lamp has the power of 100 watts, the total power is 6000 W • The and the total voltage is 120 V • We then find the answer to be #1, 5 A

Part A #20 • The known variables are voltage (4. 5 V) electrical energy, or work (1950 J) and time (1 hr) • The unknown is the resistance, R • The formula is • And we need time in seconds, so 1 hr is 3600 secs • Know we plug in the numbers to • The answer is #3, 37. 4 ohms find the resistance

Part A #21 •

Part A #22 • The amplitude of a wave is the maximum displacement of a particle, or how high/low the wave goes from its rest point • So the distance between A and D, or A and E shows the amplitude • The answer is #3, A and E

Part A #23 • In phase means the two points are 0˚ or 360 ˚ apart • Or they show two points in the same position • So in the diagram, point C is in • So for example, the points shown phase with point P below are in phase • The answer is #3, C

Part A #24 •

Part A #25 •

Part A #26 •

Part A #27 • We know electromagnetic waves do not need a medium to travel through • Radio waves and infrared waves are both also electromagnetic • So sound is the only option that is not electromagnetic, and sound needs a vacuum to travel through • So the answer is #4, sound

Part A #28 • When vibrations or wave energy is transferred from one object to another, this is called resonance • So when the energy of the car at a certain speed causes the glove box to vibrate, energy is being transferred • This is resonance • The answer is #3, resonance

Part A #29 • Diffraction is caused when a wave passes through an opening, and this causes the waves to spread out • The smaller the opening, the greater diffraction • So the answer would be #1, 0. 2 mm

Part A #30 • Constructive interference is when two waves meet and form a new wave with a greater amplitude • When the waves meet, the greatest interference would be if they met at the same point • So the answer is #1, 0˚

Part A #31 • When a source of sound is moving, the observed frequency (pitch) from a fixed point appears • So the answer is #4, lower in to change pitch • For example when a siren on a car is moving toward someone, it sounds like the pitch is getting higher • So when the whistle is moving away from the student, the observed sound is lower in pitch

Part A #32 •

Part A #33 •

Part A #34 • Light is on the reference table as an electromagnetic wave • It is also however considered a particle because it has tiny ‘packets’ of energy called photons • So light is a particle and a wave • The answer is #3, both

Part A #35 •

Part B-1 #36 •

Part B-1 #37 •

Part B-1 #38 • To understand this question, we can draw it out • We then draw out the resultant velocity • We use Pythagorean theorem to find the resultant • We find the answer to be #2, 2. 5 m/s

Part B-1 #39 •

Part B-1 #40 •

Part B-1 #41 • We can draw out a picture for this question • And we also need to understand that when you throw a ball up, it starts with a velocity of 0 m/s and • So from this we can get the increases answer to be #4 • Then at the peak of the throw, the ball stops and beings to fall, going into a negative velocity

Part B-1 #42 • We know the momentum of a system is equal to the momentum after • So if A has more momentum to the right and it collides with B which has a little less momentum to the left • The answer is #2 • We can assume that the momentum will be a small amount to the right

Part B-1 #43 • We can draw out a pendulum for this • We see as the pendulum is released from the side, its height decreases • The formula for potential energy is PE=mgΔh it also increases • So as height decreases, PE decreases • So the answer is #4 • But, after it reaches the low point,

Part B-1 #44 • The formula for power is P=Fv • ‘v’ being the speed or velocity of the elevator • So, if speed increases, then the power will also increase • This makes a direct relationship • So the answer is #1

Part B-1 #45 • A baryon is a subatomic particle that has an odd number of valence quarks • By looking at the reference table we see quarks are amounts of electrons • And the only option without an even number is option 3 • So the answer is #3, -1 e and +1 e

Part B-1 #46 • Planks constant is the amount of energy a photon carries with the frequency of its electromagnetic wave • So from this we know that the answer must be #1, plank’s constant

Part B-2 #47 • We know electric field lines flow from positive to negative • So if we draw the two plates, the field lines will look like this:

Part B-2 #48 •

Part B-2 #49 -

Part B-2 #50&#51 • We can use the data points from the previous question to answer these • We can make a graph where frequency is the x and wavelength is the y • Once the points are plotted, we connect them with a curved line

Part B-2 #52 •

Part B-2 #53 • We know the sled is moving at a constant velocity, meaning no acceleration • This means it is in equilibrium and the horizontal force is equal to the frictional force • So from the previous answer we know the horizontal force is 52 N • And therefore the frictional force has to be 52 N

Part B-2 #54 •

Part B-2 #55 • • the projectile is launched at an angle of 30˚ Projectiles launch and rise, and at the top stop, then start to fall Looking like a parabola So the path would look like this:

Part B-2 #56 • When you increase the angle of launch from 30 to 45 degrees, and the initial velocity is the same • The altitude will increase

Part B-2 #57 • Because the angle of launch is changed from 30 to 45 degrees, the altitude increases • But the horizontal distance will decrease

Part B-2 #58 • The formula for resistance is • And we know the voltage is 12 V and the current is 5 A • So we can solve for the resistance using these

Part B-2 #59 • The formula for current can be derived from the formula for resistance • We know the voltage is 12 V and the resistance is 3 ohms • So we Can solve for the unknown to find the current

Part B-2 #60 • We can use the formula for the total resistance • And we know the total resistance is 2. 4 ohms, and the first resistor is 3 ohms • So we can solve for the equation to find the unknown resistance

Part C #61 • The normal force is the force up on an object supporting another object, its equal to the weight of the object • For example, the box’s normal force is acting up from the surface • And if the box weighs 20 N, then the normal force is 20 N • And if 1 cm is equal to 4 N, the vector would be 5 cm • So we can draw a vector perpendicular to the surface of 5 cm

Part C #62 • The formula for frictional force is • To find mu, we can look it up in the reference table • The box is moving so we need kinetic coefficient of friction • The mu for kinetic wood on wood is 0. 30 • And the normal force is 20 N • So we can solve the equation to find the frictional force

Part C #63 • The net force is the total of all force acting on an object • We know the normal force, 20 N the horizontal force is 8 N the frictional force is 6 N and the weight is 20 N • We can draw this out in a diagram • So we can see that the forces equal up to a net force of 2 N

Part C #64 •

Part B-2 #65 • The formula for acceleration is F=ma • The ‘F’ being the net force of 2 N and the ‘m’ being the mass of 2 kg • We can solve for the unknown ‘a’ • and plug in the variables to find the acceleration 1 m/�� ^2

Part C #66 •

Part C #67 • The formula for gravitational PE is PE=mgΔh • We know the PE of the spring was 0. 19 J, and we know the mass of the toy is 0. 020 kg, and ‘g’ is -10 m/s^2 • So if we set the equation equal to 0. 19 J , we can solve for the unknown of max height, ‘h’ • To find the max height of 0. 97 m

Part C #68 • For this problem you need a protractor to measure the angle • From measuring, we see the angle to be about 17˚

Part C #69 • To find the angle of refraction, we can use this formula: • From the ref. tables we know the ‘n, ’ the index of refraction for air is 1. 00 and the ‘n’ for fused quartz is 1. 46 • And we know the angle of incidence is 17˚ • So we can solve for the unknown to find the angle of refraction

Part C #70 • We know from the previous question that the angle of refraction is 12˚ • So to draw this we need to use a protractor and ruler

Part C #71 • So for this one we know the angle of incidence=angle of reflection • So both angles should be about 17˚ • Use a straightedge and protractor

Part C #72 •

Part C #73 •

Part C #74 • To find this we can look at the reference tables for the energy levels of a hydrogen atom • And the photon has an energy of 2. 08 e. V • So if we look on the table, we see that value is in the 3 rd level • So n=3 is the answer

DONE!