A red train traveling at 72 km/h and a green train traveling at 144 km/h are headed toward each other along a straight, level track. When they are 840 m apart, each engineer sees the other's train and applies the brakes. The brakes slow each train at the rate of 1.0 m/s2. Is there a collision? If so, give (a) the speed of the red train, (b) the speed of the green train, and (c) the separation between the trains when they collide (0 m). If not, give (a) the speed of the red train (0 m/s), (b) the speed of the green train (0 m/s), and (c) the separation between the trains when they stop.
In: Physics
Anna, Anh and Amir are each given a sample of an unknown polymer and asked to calculate the density of their sample by measuring the mass and volume to determine if it could be polyaniline. They find a published value for the density of polyaniline to be 1.33 g cm-3.
Amir quotes his final experimental value of the density of his sample with its uncertainty to be 1.36 ± 0.01 g cm-3.
Select as many of the following statements that would be supported by Amir’s result.
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The sample may be polyaniline, but contains other substances which are ONLY less dense than polyaniline. |
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The sample is polyaniline. |
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The sample may be polyaniline, but the uncertainty has been underestimated. |
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The published value for the density of polyaniline is incorrect. |
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The equipment used to measure the volume is not precise enough to determine whether or not the sample is polyaniline. |
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The equipment used to measure the volume is inaccurate. |
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The sample is not polyaniline. |
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The equipment used to measure the mass is not precise enough to determine whether or not the sample is polyaniline. |
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The equipment used to measure the mass is inaccurate. |
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The measurements are not precise enough to determine whether or not the sample is polyaniline. |
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The sample may be polyaniline, but contains other substances which are ONLY more dense than polyaniline. |
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The sample may be polyaniline, but a systematic error may be present in the technique. |
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The equipment used to make the measurements are inaccurate. |
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The sample may be polyaniline, but contains some other substances which are less dense than polyaniline. |
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The sample may be polyaniline, but contains some other substances which are more dense than polyaniline. |
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The measurements are precise enough to determine whether or not the sample is polyaniline. |
In: Physics
A stationary nucleus of charge Q, radius R of mass M is divided
into two daughter nuclei of
the same size and charge, which repel each other to innite distance
apart after the fission.
Assume the charge density p remains the same before and after the
nuclear fission. (i)How
much kinetic energy is generated.(ii)What will be the mass of
daughter nuclei ?
(b)How much energy would be generated from the nuclear fission of
one mole of a nuclei with
Z = 92, R = 1:0fm(Assume the nuclear fission takes place as
described in part (a)).
In: Physics
A roller coaster is created with a hill of height 125 m and a loop with radius 45m. To make the crowds swoon, a new cart is brought in: a hollow sphere of mass 250kg and radius 2m, capable of carrying four passenger of total mass, 400kg.
The hollow sphere is capable of carrying passengers around the roller coaster separately. Friction although present is mostly negligible.
1.1 What is the initial energy of the system if the cart is released from rest?
1.2 What is the speed of cart when it reaches the bottom of the hill?
1.3 What is its speed at the top of the roller coaster loop?
1.4 What is the minimum speed to get around the loop? (Does it change or is it still the same?)
1.5 If the hollow sphere is replaced by a hollow disk with same mass and radius as the sphere, does the
speed in 1.4 change?
In: Physics
In the figure, a French submarine and a U.S. submarine move toward each other during maneuvers in motionless water in the North Atlantic. The French sub moves at speed vF = 47.00 km/h, and the U.S. sub at vUS = 73.00 km/h. The French sub sends out a sonar signal (sound wave in water) at 1.000 × 103 Hz. Sonar waves travel at 5470 km/h. (a) What is the signal’s frequency as detected by the U.S. sub? (b) What frequency is detected by the French sub in the signal reflected back to it by the U.S. sub?
In: Physics
At t = 0, one toy car is set rolling on a straight track with initial position 16.0 cm, initial velocity -3.9 cm/s, and constant acceleration 3.00 cm/s2. At the same moment, another toy car is set rolling on an adjacent track with initial position 10.5 cm, initial velocity 5.60 cm/s, and constant zero acceleration.
(a) At what time, if any, do the two cars have equal speeds? (Enter NA if the cars never have equal speeds.) 3.17 s
(b) What are their speeds at that time? ) 5.6 cm/s
(c) At what time(s), if any, do the cars pass each other? (If there is only one time, enter NA in the second blank. If there are two times, enter the smaller time first. If they never pass, enter NA in both blanks.)
(d) What are their locations at that time? (If there is only one position, enter NA in the second blank. If there are two positions, enter the smaller position first. If they never pass, enter NA in both blanks.) cm cm
In: Physics
b) Explain the process of radioactive decay and how radioactive half-lives are used to find the age of certain materials.
In: Physics
A uniform electric field between two parallel plates has a magnitude of 20 N/C and directed downward. Draw the E-field indicating +/- signs which plate is positive and which plate is negative?
In: Physics
A .22 rifle bullet is fired in a horizontal direction with a muzzle velocity of 900 ft/sec. In the absence of air resistance, how far will it have dropped in traveling a horizontal distance of (a) 50 yd? (b) 100 yd? (c) 150 yd? (d) How far will it drop in one second?
In: Physics
A proton, moving with a velocity of vii, collides elastically with another proton that is initially at rest. Assuming that after the collision the speed of the initially moving proton is 1.60 times the speed of the proton initially at rest, find the following.
(a) the speed of each proton after the collision in terms of vi
initially moving proton _______________ x v_i
initially at rest proton _______________ x v_i
(b) the direction of the velocity vectors after the collision (assume that the initially moving proton scatters toward the positive y direction)
initially moving proton _______________ degrees relative to +x-axis
initially at rest proton _______________ degrees relative to +x-axis
In: Physics
An ancient club is found that contains 130 g of pure carbon and has an activity of 6.5 decays per second. Determine its age assuming that in living trees the ratio of (14 C /12 C ) atoms is about 1.20 × 10^ − 12 . Note that the half life of carbon-14 is 5700 years and the Avogadro number is 6.02 × 10^23 .
In: Physics
3.3 L and C with non-vacuum filler
If we fill the space between the plates of a capacitor with an insulator the capacitance changes by a factor k called the dielectric constant due to a change in the electric field. A similar effect is observed if we fill the inner volume of a coil acting as a solenoid (the core of the solenoid), only the inductance changes due to a change in the magnetic field. Let us assume when we fill the core with some matter. The inductance will change from L to L
In: Physics
A solid metal ball is placed in an external electric field of magnitude 300 N/C. The electric field at the center of the ball is
a. zero.
b. 300 N/C.
c. 300 V/m.
d. 150 N/C.
(please show work)
In: Physics