A ball is dropped from a rooftop of a building and falls for two seconds. The acceleration of gravity is 9.8 m/s2 . The ball is referred to at the two second time. The acceleration of the ball in m/s2 is
a. 0 d. 6
b. 4.9 e. none of these
c. 9.8
C
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Which reason best explains why both Venus's and Mars's atmospheres are primarily carbon dioxide, but Earth's is much less than 1% carbon dioxide?
A. Each planet has a significantly different surface temperature. B. Venus and Mars, being smaller than Earth, can't retain the same mixture of gases as Earth. C. Earth's rocks had much less carbon and oxygen in them. D. Plant life has existed on Earth for an extended amount of time.
Bright blue stars are typical of young ________ star clusters
Fill in the blank(s) with correct word
One mole of hydrogen, one mole of nitrogen and one mole of oxygen are held in a 22.4 × 10^3 cm3 enclosed vessel at 20°C. The pressure in the vessel, in N/m2, is
a. 109. b. 304. c. 326. d. 1.09 × 10^5. e. 3.26 × 10^5.
Energy Conservation With Nonconservative Forces: As shown in the figure, a 1.45-kg block is held in place against the spring by a 21-N horizontal external force. The external force is removed, and the block is projected with a velocity v1 = 1.2 m/s as it separates from the spring. The block descends a ramp and has a velocity v2 = 2.1 m/s at the bottom. The track is frictionless between points A and B. The block enters a rough section at B, extending to E. The coefficient of kinetic friction between the block and the rough surface is 0.29. The velocity of the block is v3 = 1.4 m/s at C. The block moves on to D, where it stops. How much work is done by friction between points B and C?
style="vertical-align: 0.0px;" height="148" width="576" /> A. -1.8 J B. -3.6 J C. -14 J D. -6.4 J E. -7.0 J