If originally there were X atoms of radioactive isotope present and now there are only X/4 atoms, how many half-lives have elapsed?
A) 1
B) 4
C) 2
D) 3
C
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One-third as much net force is exerted on object A as on object B. The two objects have the same mass. How do their accelerations compare?
A) Object A has one-sixth as much acceleration as object B. B) Object A has three times as much acceleration as object B. C) Object A has one-third as much acceleration as object B. D) They both have the same acceleration. E) It is impossible to answer this without further information about the two objects.
A 12.0-kg mass is placed on a 29.0° incline and friction keeps it from sliding. The coefficient of static friction in this case is 0.660, and the coefficient of sliding friction is 0.546 . The mass is given a shove causing it to slide down the incline. What is the frictional force while the mass is sliding?
a. 57.0 N b. 102.9 N c. 56.2 N d. 67.9 N e. 10.5 N
Two metal rods, one silver and the other gold, are attached to each other end-to-end. The free end of the silver rod is immersed in a steam chamber at 100°C, and the free end of the gold rod in an ice water bath at 0°C
The rods are both 5.0 cm long and have a square cross-section that is 2.0 cm on a side. No heat is exchanged between the rods and their surroundings, except at the ends. What is the temperature at the point where the two rods are in contact with one another? The thermal conductivity of silver is 417 W/m ? K, and that of gold is 291 W/m ? K. A) 47°C B) 39°C C) 41°C D) 59°C E) 53°C
An aluminum bar (E 5 70 GPa, ? 5 0.33) of diameter 20 mm is stretched by axial forces P, causing its diameter to decrease by 0.022 mm. The load P is approximately:
(A) 73 kN
(B) 100 kN
(C) 140 kN
(D) 339 kN
