During World War I, Germany used a "Big Bertha" cannon to hurl shells into Paris 30 miles away. This gun also had a very long barrel. What was the reason for using a long barrel in these guns?
A) to increase the force exerted on the bullet due to the expanding gases from the gunpowder
B) to reduce the force exerted on the bullet due to the expanding gases from the gunpowder
C) to reduce frictional losses
D) to exert a larger force on the shells
E) to allow the force of the expanding gases from the gunpowder to act for a longer time
E
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In what ways is Earth different from the other terrestrial planets?
A) Its lithosphere is broken into plates that move around. B) It has a much higher percentage of oxygen in its atmosphere. C) Most of its surface is covered with liquid water. D) Life can be found almost everywhere on its surface. E) All of the above are true.
How are interstellar bubbles of hot, ionized gas made?
A) by the collapse of a gas cloud to form stars B) by the ejection of planetary nebulae from low-mass stars C) by the winds of massive stars and supernovae explosions D) by collisions between the Milky Way and satellite dwarf galaxies E) by the rapidly rotating magnetic fields of pulsars
Study this diagram that summarizes the eras of the universe. Which of the following statements is not true?
A) The electroweak era was the longest lasting of all the eras in the history of the universe. B) The total time during which the universe went through the Planck era, GUT era, electroweak era, and particle era was less than the time it takes you to blink your eyes. C) Whole atoms with both electrons and nuclei were not stable until the universe was about 380,000 years old. D) Most of the helium in the universe was produced before the universe was about five minutes old.
Which of the following is not a unit of pressure?
a. atmosphere b. psi c. N/m2 d. mm of mercury e. pascal f. none of the above Indicate whether the statement is true or false