## Thursday, August 26, 2021

### More Physics Problems From Past GRE Papers

TIME:  30  Minutes

1) A sub-atomic particle moving at a constant speed of 6 x 10 6 m/s enters a region with an electric field where it's decelerated at a rate of 1.2 x 1014 m/s/s. Find the linear distance the particle travels before coming to rest (in cm).

2) Two particles of mass, m and M, are initially at rest and infinitely separated from each other. At any later instant, find their relative velocity vR  of approach attributable to gravitational attraction.

3) A current of 5A resides in a 10-ohm resistance for 4 minutes. . How many coulombs pass through any cross section of the resistance in this time?

4) The effective value of a sinusoidal alternating emf is equal to its maximum value multiplied by what?

5) If it requires two joules of work to move 20 coulombs from point A to point B, find the potential difference between A and B in volts.

6) A parallel plate capacitor with 0.3 cm thickness of air between the plates has a capacitance of 15  mmF (micro-micro-Farads). Find the new capacitance when the air is replaced by mica (dielectric constant k = 6)

7) Classically speaking, the electron of a hydrogen atom moves in a circular orbit or radius 0.53 x 10-10m with a frequency f = 6.6 x 1015 /s. Find the current associated with this orbit.

8) A small object is placed 10 cm in front of a plane mirror. If you stand behind the object, 30 cm from the mirror, and look at the image - for what distance must you focus your eyes?

9) A thin, double convex lens has radii of curvature of magnitude 40 cm and is made of glass with refractive index n = 1.65. Find the focal length.

10) Consider the nuclear transformation reaction below:

1.2 MeV + 7N14 + 2He4 -> ? + 1H1

The component needed to fill in the position on the right hand side is:

A) 8 O 16 B) 9F 16 C) 6 N 16 D) 8 O 17 E) 8 O 16

11) Determine the velocity of a meson whose kinetic energy is 4 MeV. (The rest mass of a mu meson is 106 MeV)

12) Consider two unequal masses connected by a string which passes over a frictionless and massless pulley. (Let m1 be less than m2. ) Write the Lagrangian for the system.

13) For the same system in #12, find a, the acceleration of the masses m1 and m2.

14) Let T1 and T2 be the temperatures of two reservoirs. If T1 > T2 and we operate a Carnot engine between the reservoirs, what would be the efficiency, as a function of T1 and T2?

15) Determine the different values for the total orbital angular momentum quantum number of a two-electron system for which the individual quantum numbers are L1 = 3 and L2 = 2.
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