One material used in nuclear bombs is 239Pu, with a half-life of 24,000 years. How long must we wait for a buried stockpile of this substance to decay to 1/1000 of its original activity?
A) 1,200,000 years
B) 240,000 years
C) 150,000 years
D) 82,000 years
E) 1,500 years
B
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What was the purpose of the LCROSS mission?
a. To determine if lava still flowed beneath the crust b. To generate an altitude map of the Moon's surface c. To photograph geological features of the Moon d. To photograph geological features of the Moon e. To determine if there is water ice buried in soil of the Moon's south pole
Two long parallel wires that are 0.30 m apart carry currents of 5.0 A and 8.0 A in the opposite direction. Find the magnitude of the force per unit length that each wire exerts on the other wire and indicate if the force is attractive or repulsive
(?0 = 4? × 10-7 T ? m/A) A) 2.7 × 10-5 N repulsive B) 7.2 × 10-5 N repulsive C) 3.4 × 10-5 N attractive D) 2.7 × 10-5 N attractive E) 7.2 × 10-5 N attractive
The efficiency of an engine can be defined as the
A. ratio of work done to energy input. B. ratio of work done to energy exhausted. C. ratio of heat exhausted to heat intake. D. total amount of work performed.
A 20-kg object is resting at the top of a table 1.3 m above ground level. The object is then picked up and moved to a height of 7.7 m above ground level. What is the change in the gravitational potential energy of this object?
