Which element represented most of the atoms in the early Universe?
a. helium
b. hydrogen
c. oxygen
d. carbon
e. nitrogen
b
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In partially stabilized zirconia (ZrO2), the addition of materials such as MgO or CaO lowers the temperature of the _________transformation of the tetragonal to the monoclinic phase.
Fill in the blank(s) with the appropriate word(s).
Gasoline is useful in cars because it has
A) chemical potential energy. B) electrical potential energy. C) kinetic energy. D) gravitational potential energy. E) radiative energy.
Angular Momentum: A solid, uniform, horizontal disk with a diameter of 2.0 m and a mass of 4.0 kg freely rotates at 36 rpm about a vertical axis through its center. A small 0.50-kg stone is suddenly dropped onto the disk and sticks to the disk at a distance of 80 cm from the axis of rotation. The figure shows before and after views.(a) Before the stone fell, what was the moment of inertia of the disk about its central axis?(b) After the stone stuck, what was the moment of inertia of the system about the same axis?(c) What is the angular velocity of the disk (in rpm) after the stone fell onto the disk?
What will be an ideal response?
Which of the following best describes the current status of the evidence concerning whether life has ever existed on Mars?
A) Mars probably once had a habitable surface, but we do not know if it had life. B) Clear evidence strongly suggests that life once existed on Mars. C) Clear evidence indicates that Mars never had conditions favorable to life. D) Although current evidence is mixed, ongoing studies should ensure that we will have a definitive answer to the question of whether life ever existed on Mars within about five years.