The amount of meat in prehistoric diets can be determined by measuring the ratio of the isotopes nitrogen-15 to nitrogen-14 in bone from human remains. Carnivores concentrate 15N, so this ratio tells archaeologists how much meat was consumed by ancient people. Suppose you use a velocity selector to obtain singly-ionized (missing one electron) nitrogen atoms of speed 8.95 km/s and bend them along a semicircle within a uniform magnetic field. The 14N atoms travel along a semicircle with a diameter of 27.5 cm . The measured masses of these isotopes are 2.32×10−26 kg (14N) and 2.49×10−26 kg for (15N). Find the separation of the 14N and 15N isotopes at the detector.
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A football kicker can give the ball an initial speed of 25.0 m/s. What are the (a) least and (b) greatest elevation angles at which he can kick the ball to score a field goal from a point 50.0 m in front of goalposts whose horizontal bar is 3.44 m above the ground? When doing this, you may want to research some trig identities to get a formula involving only tangent functions. Also, since there are two values of angle that will work, maybe the quadratic formula is involved.
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Suppose the Earth is really flat. Shaped like a penny, it has one side that faces the Sun at all times. Suppose this Earth is the same temperature everywhere (including the side that faces away from the Sun). Neglect any radiation losses off the rim of the Earth and assume there is no albedo or greenhouse effect. Treating it as a perfect blackbody, estimate the temperature of this new, flat Earth.
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(iii) A consequence of the Free Electron approach is that the electron mass me effectively becomes a variable, the so-called effective mass, me * , which is governed by the curvature of the Ek vs. k function. Show that where the curvature of this function is large the effective mass is small. [4 marks]
(iv) It is often found that some ‘useful’ semiconductors such as silicon or gallium arsenide have bands which show a high degree of curvature, whereas many insulators do not. Discuss how this influences the properties of each type of material.
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Answer it in detail (1-2 paragraphs)
1. Define a reference frame and then an inertial reference frame. Give example of both inertial and non-inertial reference frames.
2. Explain the concept of time dilation. What is the twin paradox?
3. Explain why it is impossible for an object to travel at the speed of light (Hint: evaluate the energy of the object)
4. Discuss the importance of the photoelectric effect in the context of quantum physics.
5. What is the de Broglie wavelength? List at least one experimental evidence the matter exhibits wave characteristics.
6. State Hesisenberg's uncertainty principle.
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For higher accuracy, should R decade be large or small? Why?
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Explain why there is more danger when you fall and bounce as opposed to falling without bouncing.
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Laser light from argon ion laser of wavelength 488.0 nm passes through a diffraction grating. The first bright spots occur at an angle 6.726 degree left and right from the central maximum. How many additional pares of bright spots are there beyond the first bright spots?
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The solar wind consists of protons, electrons and other heavier irons and they have velocities of several hundred km per second. Moving charged particles experience a force when in an external magnetic field. The Earth's magnetic field at the equator has a value of approximately 3 x 10^{-5} T and is directed to the north. This field strength extends into the space above the earth. Consider a solar wind proton moving at 5 x 10^{5} m/s that approaches the earth from outer space along a line toward the center of the earth that lies on the plane of the equator. In what direction will the proton be deflected? Will it reach the earth's surface? What if the particle were an electron? Why is the Earth's Magnetic field important to life on the Earth?
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A converging lens has a focal length of 9.0 cm. Locate the images for the object distances of (a) 20.0 cm, (b) 10.0 cm, and (c) 5.00 cm, if they exist. For each case, state whether the image is real or virtual, upright or inverted, and find the magnification.
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An 90mm focal-length lens is used to focus an image on the film of a camera. The maximum distance allowed between the lens and the film plane is 130mm .
A. How far ahead of the film should the lens be if the object to be photographed is 2.9
m away?
B. How far ahead of the film should the lens be if the object to be photographed is 1.1
m away?
C. What is the closest object this lens could photograph sharply?
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describe how you can use a magnet to exert both a contact force and a non-contact force on another magnet?
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A family comes home from a long vacation with laundry to do and showers to take. The water heater has been turned off during vacation. If the water heater has a capacity of 49.1 gallons and a 4610 W heating element, how much time is required to raise the temperature of the water from 18.8°C to 62.1°C? Assume that the heater is well insulated and no water is withdrawn from the tank during this time.
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The position of a 0.30-kg object attached to a spring is described by x = (0.24 m) cos(0.8πt). (Assume t is in seconds.) (a) Find the amplitude of the motion. 0.24 Correct: Your answer is correct. m (b) Find the spring constant. 1.9 Correct: Your answer is correct. N/m (c) Find the position of the object at t = 0.33 s. 0.16 Correct: Your answer is correct. m (d) Find the object's speed at t = 0.33 s. Incorrect: Your answer is incorrect.
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