A baseball is hit with a bat and, as a result, its direction is completely reversed and its speed is doubled. If the actual contact with the bat lasts 0.45 s,
what is the ratio of the magnitude of the average acceleration of the ball to its original speed?
A) 6.7 s-1
B) 4.4 s-1
C) 2.2 s-1
D) 0.15 s-1
A
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A coil lies flat on a horizontal table top in a region where the magnetic field points straight down. The magnetic field disappears suddenly
When viewed from above, what is the direction of the induced current in this coil as the field disappears? A) counterclockwise B) clockwise C) clockwise initially, then counterclockwise before stopping D) counterclockwise initially, then clockwise before stopping E) There is no induced current in this coil.
Carts A and B have equal masses and travel equal distances on straight frictionless tracks while a constant force F is applied to A, and a constant force 2F is applied to B. The relative amounts of work done by the two forces are related by
a. WA = 4 WB. b. WA = 2 WB. c. WA = WB. d. WB = 2 WA. e. WB = 4 WA.
Which one of the following is TRUE?
a) Irregular galaxies rarely have star formation taking place in them. b) Galaxy collisions destroy most of the stars in the galaxies involved. c) Most elliptical galaxies contain only young stars. d) Most galaxies appear to be approaching the Milky Way Galaxy. e) There is a supermassive black hole in the center of the Milky Way Galaxy
A solenoid of length l = 0.7 m and radius R = 5 cm stores an amount of energy U = 6 × 10-6 J when a current I = 0.4 A passes through it. What is the winding density of the solenoid?
A) 865 turns /m B) 472 turns/m C) 1078 turns/m D) 104 turns/m E) 327 turns /m