A 20-m long steel wire (cross-section 1.0 cm2, Young's modulus 2.0 × 1011 N/m2), is subjected to a load of 25 000 N. How much will the wire stretch under the load?
A. 0.25 cm
B. 2.5 cm
C. 12.5 cm
D. 25 cm
E. 1.25 cm
Answer: B
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A proton is moving perpendicular to a magnetic field at 
and experiences a magnetic force of magnitude
N. What is the magnitude of the magnetic field?
A. 0.52 T
B. 
C. 
D. 
E. 
Which of the following best explains the phenomenon of black hole evaporation?
A) Due to high temperatures in the accretion disk around a black hole, material evaporates from the black hole like water evaporating from the ocean. B) Particles (or antiparticles) are occasionally ejected from within the event horizon, causing the black hole to lose mass. C) Particles (or antiparticles) are created by a quantum mechanical effect near, but outside, the event horizon of the black hole. The law of conservation of energy maintains that the black hole must lose energy to "pay" for the creation of this mass. D) Virtual particles created near the black hole are constantly annihilating each other, causing a very high temperature even if the black hole has no accretion disk. This high temperature provides escape velocity for the virtual particles, causing the entire "cloud" of virtual particles to expand away into space. E) Black hole evaporation is a virtual process, meaning that it has been theorized by astrophysicists but doesn't really occur.
Gravity waves are produced when a mass accelerates
Indicate whether the statement is true or false
In the context of life in the universe, which of the following discoveries of astronomy suggests that the processes that formed life on Earth could have occurred elsewhere?
A) the universe is very old B) the laws of physics are the same everywhere C) the universe is very large D) the chemical elements that make up life on Earth are common