The simplest life forms appeared on Earth when it was how old?
A) five million years
B) one billion years
C) 2.5 billion years
D) 3.5 billion years
E) 4.5 billion years
B
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Electric field lines can cross only if both positive and negative charges are involved
Indicate whether the statement is true or false
A 3.0-kg mass sliding on a frictionless surface has a velocity of 5.0 m/s east when it undergoes a one-dimensional inelastic collision with a 2.0-kg mass that has an initial velocity of 2.0 m/s west. After the collision the 3.0-kg mass has a velocity of 1.0 m/s east. How much kinetic energy does the two-mass system lose during the collision?
a. 22 J b. 24 J c. 26 J d. 20 J e. 28 J
Each of the following general equations illustrates what basic type of chemical reaction?
a. AB + CD ? AD + CB ______________ b. A + B ? AB ______________ c. A + BC ? AC + B ______________ d. AB ? A + B ______________
Which of the following telescopes is most suitable for observing cool gas clouds?
A. radio telescope B. visible-light telescope C. X-ray telescope D. All of these choices are correct. E. Cool gas clouds cannot be observed by telescopes.