A 6.0-kg block slides along a horizontal surface. If µk = 0.20 for the block and surface, at what rate is the friction force changing the mechanical energy of the block at an instant when its speed is 4.0 m/s?
a. -59 W
b. -47 W
c. -71 W
d. -82 W
e. +71 W
B
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Albert Michelson is primarily remembered for
A) proving length contraction. B) not being able to detect an "ether". C) his theory published in 1916. D) proving that the speed of light is not constant. E) proving time dilation.
In a completely filled atomic shell,
a. the intrinsic spin of the electrons does not produce a resultant magnetic moment. b. the orbital motion of the electrons does not produce a resultant magnetic moment. c. the atom will be an alkali metal. d. only (a) and (b) are correct. e. none of the above are correct.
Force on a Moving Charge: A proton, moving east, enters a magnetic field. Because of this magnetic field the proton curves downward. We may conclude that the magnetic field must have a component
A. towards the south. B. towards the north. C. towards the west. D. upward. E. downward.
Waves on a String: A string of mass m is under tension, and the speed of a wave in the string is v. What will be the speed of a wave in the string if the mass of the string is increased to 2m but with no change in the length or tension?
A. v/2
B. v/
C. v
D. 2v
E. 4v