When jumping straight down, you can be seriously injured if you land stiff-legged. One way to avoid injury is to bend your knees upon landing to reduce the force of the impact. A 67.3-kg man just before contact with the ground has a speed of 3.81 m/s. (a) In a stiff-legged landing he comes to a halt in 2.92 ms. Find the magnitude of the average net force that acts on him during this time. (b) When he bends his knees, he comes to a halt in 0.255 s. Find the magnitude of the average net force now. (c) During the landing, the force of the ground on the man points upward, while the force due to gravity points downward. The average net force acting on the man includes both of these forces. Taking into account the directions of the forces, find the magnitude of the force applied by the ground on the man in part (b).

Enter numerical answers with THREE SIGNIFICANT FIGURES.

A soap bubble of uniform thickness has an index of refraction of 1.53, and is illuminated by light with a wavelength of 580. nm.

a) Calculate the wavelength of the light in the soap bubble. (Enter THREE sig figs)
nm


Which two rays will interfere with each other?


How many ½ λ shifts must be considered, and where do these shifts (if any) occur? Briefly explain your answer.



c) What is the minimum thickness of a soap bubble such that the light is strongly reflected? (Enter THREE sig figs)
nm

Question 10

The statements in the following list all refer to Quantum Physics. Check the boxes of the THREE CORRECT statements.

1. In the photoelectric effect, the maximum energy of the emitted electrons depends on the frequency of the incoming electromagnetic radiation and not on the intensity. There is a threshold frequency below which no electrons are emitted.

2. Electrons can behave both as particles and as waves.

3. It is not necessary to know the potential energy function of a particle in order to to solve the time-independent Schrödinger equation and obtain the wave function describing it.

4. The allowed energy levels of a particle in an infinite square well are equally spaced.

5. In spectroscopic notation, the letters 's', 'p', 'd', etc. are used to identify the magnetic quantum number m_l associated to a state or energy level.

6. An atom can be stimulated to make a transition from a higher to a lower energy level by a photon of the appropriate energy.

1. Parallel light rays pass through a converging lens and

a. stay parallel

b. all travel to a point that is at a defined distance away from the lens

c. diverge rapidly

d. reflect back to a point in front of the lens

2. For a lens with a given focal length of 10 cm and an object placed 15 cm in front of it, where is the image located?

a. 30 cm

b. 10 cm c. 20 cm

d. 25 cm

3. For problem number 2, what is the magnification?

a. M = 1/2

b. M = -1/2

c. M = 2

d. M = -2

4. For problem number 2, describe the relation of the image height to the object height. Is the

a. image height smaller than the object height

b. image height larger than the object height

c. image height and object height are equal

5. Describe the image that is formed in problem #2. Is it?

a. real and upright

b. real and virtual

c. real and inverted

d. virtual and inverted

6. For a lens with a given focal length of 10 cm and an object placed 5 cm in front of it, where is the image located?

a. 10 cm behind the lens

b. 10 cm in front of the lens

c. 2 cm in front of the lens

d. 2 cm behind the lens

7. For problem number 6, what is the magnification?

a. M = ½

b. M = -1/2

c. M = 2

d. M = -2

8. The letter “B” in the above diagram of a camera is identified as the

a. film

b. shutter

c. lens

d. aperture

9. The letter “D” in the above diagram of a camera is identified as the

a. film

b. shutter

c. lens

d. aperture

10. To create a virtual magnified image of an object,

a) the object must be at the focal point of a concave lens.

b) the object must be just outside the focal point of a convex lens.

c) the object must be very far from a convex lens.

d) the object must be within the focal point of a convex lens.

A point charge of -1C is placed in the center of a spherical shell of radius R and with surface charge density σ=1C/2πR^2.Calculate the magnitude of the electric field inside and outside the sphere. If a test charge q_0 was placed (inside and outside the sphere), what would be the magnitude of the force it would experience?

Mary spots Bill approaching the dorm at a constant rate of 2 m/s on the walkway that passes directly beneath her window, 17 m above the ground. When Bill is 120 m away from the point below her window she decided to drop an apple down to him.

A.) How long should Mary wait to drop the apple if Bill is to catch it 1.75 m above the ground, and without either speeding up or slowing down?

B.) How far from directly below the window is Bill when Mary releases the apple?

A common approximation to the interatomic forces in a material is the Lennard-Jones potential between neighboring atoms in a solid:

U(r) = A/r¹² - B/r⁶

This can be used to find various information about a solid material.

Assume that for the lattice of a particular alloy of copper, the Lennard-Jones constants are:

A = 9.08 ⨯ 10^-133 J·m¹²
B = 3.96 ⨯ 10^-76 J·m⁶

Find the following:

(a) The equilibrium distance between neighboring atoms in the copper lattice (this is called the lattice constant a).


(b) Model this as an approximate potential around the equilibrium position

U_eff(r) = (1/2)k(r-a)² + C

(i) What is the effective spring stiffness k?


(ii) What is the energy minimum C?


(c) Find the resonance frequency of a copper atom in a linear chain of atoms? [Assume only nearest neighbor interactions]


(d) Find the vibration amplitude at the temperature T = 5⁰C. Assume that the oscillator has one degree of freedom.

[ Use k_B = 1.38⨯10^-23 J/K/atom as Boltzmann's constant. ]

1. A box of mass 5kg moves to the left at a speed of 6m/s. The box is moving toward an unstretched spring of spring constant 500N/m that is attached to a barrier. If the floor is frictionless, how much does the spring compress in bringing the box to rest? If instead the floor has a coefficient of friction of 0.4, how much does the spring compress in bringing the box to rest?

Determine the magnitude of the gravitational force Mars would exert on man if he was on the surface of Mars. The mass of the man is 67.0kg . The mass of the Mars is 6.42

1. Explain the difference between linear, radial, and angular acceleration and identify which "G" force vector is most significant in normal aircraft flight.

Prelab 7: DC Circuits 1

What are the units of Resistance?

Watch the video tutorial about series and parallel circuits. Explain what ammeters and voltmeters do – Why are they hooked up to the circuit differently, and why don't they affect the circuit?

What is the resistance of a resistor when the colored bands read yellow, red, green and gold ?

What is a thermistor?

Three resistors with values of 1,488 Ohms, 1,101 Ohms and 860 Ohms are in parallel with each other in a circuit. What is the equivalent resistance of this parallel circuit?

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An automobile of mass 1500kg moving at 25m/s collides with a truck of mass 4500kg at rest. This time, the car and the truck bounce off each other completely elastically. What is the final velocity of the truck after the collision? Call the direction of the automobile before the collision positive.

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An automobile of mass 1500kg moving at 25m/s collides with a truck of mass 4500kg at rest. This time, the car and the truck bounce off each other completely elastically. What is the final velocity of the car after the collision? Call the initial direction of the automobile positive.

A block slides down a frictionless inclined ramp. If the ramp angle is 26° and its length is 29 m, find the speed of the block as it reaches the bottom of the ramp, assuming it started sliding from rest at the top.

A thin, rectangular sheet of metal has mass M and sides of length a and b. Find the moment of inertia of this sheet about an axis that lies in the plane of the plate, passes through the center of the plate, and is parallel to the side with length b. Express your answer in terms of some or all of the variables M, a, and b

Find the moment of inertia of the plate for an axis that lies in the plane of the plate, passes through the center of the plate, and is perpendicular to the axis in part A.

Express your answer in terms of some or all of the variables M, a, and b.

If matter has a wave nature, why is this wave-like characteristic not observable in our daily experiences?

Any object of macroscopic size—including a grain of dust—has an undetectably small wavelength, so any diffraction effects it might exhibit are very small, effectively undetectable. Recall historically how the diffraction of sound waves was at one time well known, but the diffraction of light was not.

Only objects of macroscopic size, like an ocean wave, actually exhibit a wave nature. Smaller, microscopic objects—including a grain of dust—do not exhibit a wave nature.    

Only objects of microscopic size, like an atom, actually exhibit a wave nature. Larger, macroscopic objects—including a grain of dust—do not exhibit a wave nature.

Any object of macroscopic size—including a grain of dust—has a large wavelength, so any diffraction effects it might exhibit are very large, too large to be detectable. Recall historically how the diffraction of sound waves was at one time well known, but the diffraction of light was not.