Charge in an Electric Field: A small object with a 5.0-?C charge is accelerating horizontally on a friction-free surface at 0.0050 m/s2 due only to an electric field. If the object has a mass of 2.0 g, what is the magnitude of the electric field?
A. 2.0 N/C
B. 4.0 N/C
C. 0.0020 N/C
D. 0.0040 N/C
E. 1.0 N/C
Answer: A
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Entropy: A 0.42-kg quantity of ethanol, in the liquid state at its melting point of -114.4°C, is frozen at atmospheric pressure. The heat of fusion of ethanol is 1.04 × 105 J/kg, and its molecular mass is 46.1 g/mol. What is the change in the entropy of the ethanol as it freezes?
A. -280 J/K B. -250 J/K C. -310 J/K D. 250 J/K E. 280 J/K
A hoop and a solid disk both have the same radius and mass and negligible thickness. Assume that they are both rotating with the same constant angular speed. Which has the higher rotational kinetic energy?
1.the hoop 2.the disk 3.They both have the same rotational kinetic energy. 4.impossible to determine
Why do we expect WIMPs to be distributed throughout galactic halos, rather than settled into the galaxy's disk?
A) WIMPs are lightweight enough that they have expanded out into the halo. B) WIMPs were produced by stars in the early stages of galaxy evolution and therefore are only found in globular clusters in the halo. C) WIMPS rarely interact with other particles and therefore cannot settle into galactic disks. D) Shock waves from generations of supernovae have blown the WIMPs out into the halo. E) WIMPs annihilate when they come into contact with ordinary matter, such as stars.
A photon of energy 4eV is incident on a metal surface whose work function is 2eV. The minimum reverse potential to be applied for stopping the emission electrons is
a) 2V b) 4V c) 6V d) 8V