An electron and a positron are located 17 m away from each other and held fixed by some mechanism. The positron has the same mass and the same magnitude of charge as those of the electron, but its charge is positive. The electron and the positron are released at the same time by the mechanism. The electron and the positron begin to speed up towards each other. What velocities should they have when they are 1.3 m away from each other?

QUESTION 1:

Two point masses are the same distance R from an axis of rotation and have moments of inertia I_A and I_B.

(a)

If I_B = 4I_A, what is the ratio

of the two masses?

=

(b)

In terms of R, at what distance from the axis of rotation should mass A be placed so that

I_A = I_B?

R

QUESTION 2:

A large grinding wheel in the shape of a solid cylinder of radius 0.330 m is free to rotate on a frictionless, vertical axle. A constant tangential force of 230 N applied to its edge causes the wheel to have an angular acceleration of 0.980 rad/s².

(a) What is the moment of inertia of the wheel?
kg · m²

(b) What is the mass of the wheel?
kg

(c) If the wheel starts from rest, what is its angular velocity after 4.60 s have elapsed, assuming the force is acting during that time?
rad/s

Apply the Pauli exclusion principle to determine the number of electrons that could occupy the quantum states described by the following.

a) n = 4, ℓ = 3, mℓ = −2

b) n = 4, ℓ = 2

c) n = 4

Your 300mL cup of coffee is too hot to drink when served at 90.0 ∘C.

A)What is the mass of an ice cube, taken from a -16.0 ∘C freezer, that will cool your coffee to a pleasant 58.0 ∘?

5. A proton and an electron are in a uniform electric field with magnitude 45 V/C. Which particle has the larger magnitude acceleration, and what is the magnitude of the acceleration? (e = 1.6×10−19 C, mp = 1.67×10−27 kg, me = 9.11×10−31 kg) A. the electron, 7.9×1012 m/s2 B. the proton, 4.3×1013 m/s2 C. the proton, 4.3×109 m/s2 D. the electron, 7.9×108 m/s2 E. the electron, 7.9×1010 m/s2

6. A +2q point charge is located at the origin (x = 0), and a –3q charge is at x = +d. What is the magnitude of the electric field at x = +2d ? Assume 1 4π0 = k. A. 7kq 2d2 B. 5kq 2d2 C. 4kq d2 D. 3kq 2d2 E. 5kq d2

A mass m = 17 kg is pulled along a horizontal floor with NO friction for a distance d =5.7 m. Then the mass is pulled up an incline that makes an angle θ = 34° with the horizontal and has a coefficient of kinetic friction μk = 0.38. The entire time the massless rope used to pull the block is pulled parallel to the incline at an angle of θ = 34° (thus on the incline it is parallel to the surface) and has a tension T =83 N.

What is the work done by tension before the block goes up the incline? (On the horizontal surface.)

What is the speed of the block right before it begins to travel up the incline?

What is the work done by friction after the block has traveled a distance x = 2.6 m up the incline? (Where x is measured along the incline.)

What is the work done by gravity after the block has traveled a distance x = 2.6 m up the incline? (Where x is measured along the incline.)

How far up the incline does the block travel before coming to rest? (Measured along the incline.)

A common solution to the wave equation is E(x,t) = A e^^i(kx+wt). On paper take the needed derivatives and show that it actually is a solution. Note that i is the square-root of -1.

Five kilograms of ammonia (NH3) undergo a refrigeration cycle
detailed as:
• Process 1-2: isothermic expansion from saturated vapor at 10ºC, to P = 3 bar with
Q = 400 kJ.
• Process 2-3: isochoric cooling to 0 ◦C.
• Process 3-4: isobaric compression.
• Process 4-1: isochoric heating.

Calculate:

a) the P −v and T −v diagrams.

b) the states table detailing P, v, T and u.
c) the process table for Q, W and ∆U.
d) the performance coefficient, β, of the cycle.

Consider two spherical shells with radii R1 < R2 with the inner shell having the potential Φ(ϑ)=Φ1×cos^2(ϑ), ϑ being the azimuthal angle in spherical coordinates. The outer shell is metallic and uncharged (Q2 = 0). Calculate the potential Φ(r) on the entire space. Thanks a lot.

1. Distinguish between inertial and accelerated frames of reference.

2.Consider two days when the air temperature is the same but the humidity is different. Which is more dense, the dry air or the humid air at the same T?

The circuit you’re making needs a 1.5?? capacitor but you only have three 1?? capacitors. Draw how you make an equivalent capacitor from the 1?? capacitors.

A heavy semi-truck collides head-on with a small, light car. Before the collision the vehicles were moving with the same speed but in opposite direction.

A. Just before the collision, was the magnitude of the momentum of the car greater, equal or less than that of the truck?

B. Just before the collision, was the kinetic energy of the car greater, equal or less than that of the truck?

C. During the collision, is the force that the car exerts on the truck greater, equal or less than the force that the truck exerts on the car?

D. During the collision, is the magnitude of the acceleration of the car greater, equal or less than the magnitude of the acceleration of the truck?

E. If the two vehicles stick together immediately after the collision, which way will they be moving, if at all?

1) why do atoms have discrete spectral lines?

2) Is it possible for different atomic transitions, in a particular atom, to give off the same colour photons?why?

3) A beam of red photons and blue photons are sent through a diffraction grating simultaneously. Sketch the diffraction pattern of both colours.

4) The spectrometer provided is able to measure angles to a precision of 1 minute (1'). Given that 60'=1degree, convert the following angles, 31degree 21' and 12degree 5', into degrees.

1. Several forces act on an object at rest. It is known that the sum of the forces acting on the object is zero. Which statement is necessarily true?
A) The object will remain stationary.
B) The object's center of mass may move in such a way that the object will roll without slipping.
C) The object's center of mass will not move, but the object may begin to rotate.
D) The object's center of mass may accelerate and the object may begin to rotate.
E) The object's center of mass may accelerate, but the object will remain in the same orientation.

2. A heavy boy and a lightweight girl are balanced on a massless seesaw. If they both move forward so that they are one-half their original distance from the pivot point, what will happen to the seesaw?
A) It is impossible to say without knowing the masses.
B) It is impossible to say without knowing the distances.
C) The side the boy is sitting on will tilt downward.
D) Nothing, the seesaw will still be balanced.
E) The side the girl is sitting on will tilt downward.

3. A cone balanced on its small end is in
A) stable equilibrium.
B) unstable equilibrium.
C) neutral equilibrium.
D) positive equilibrium.
E) negative equilibrium.

4. A sphere hanging freely from a cord is in
A) stable equilibrium.
B) unstable equilibrium.
C) neutral equilibrium.
D) positive equilibrium.
E) negative equilibrium.

5. The region from the origin to the elastic limit on an applied force versus elongation graph for a typical metal under tension is referred to as the
A) elastic region.
B) proportional region.
C) plastic region.
D) ultimate strength region.
E) breaking region.

6. The maximum elongation of a typical metal is reached at the
A) proportional limit.
B) elastic limit.
C) inelastic limit.
D) breaking point.
E) ultimate strength.

7. Strain is
A) the ratio of the change in length to the original length.
B) the stress per unit area.
C) the same as force.
D) the applied force per cross-sectional area.
E) the ratio of stress to elastic modulus.

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