A 10-m plank with a mass of 80 kg is being moved by rolling it over two cylindrical logs, each with a mass of 10 kg and a radius of 20 cm, placed 2 m from either end of the plank
As the plank is pushed, the logs roll on the ground without slipping, and the plank does not slip on the rollers. A force of 250 N is applied to the plank. What is the speed of the plank after it has moved 2 m, starting from rest? A) 1.87 m/s
B) 2.53 m/s
C) 3.43 m/s
D) 3.54 m/s
E) 2.37 m/s
C
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It can be shown that the change in entropy in heating or cooling a sample is given by the relation src="https://sciemce.com/media/4/c597f3a04fb2c30572.png" class="w-image" />C?
A. +2.93 J/K
B. +2.50 J/K
C. 0.00 J/K
D. -2.93 J/K
= mc ln 
where m is the mass of the sample, c is the specific heat of the sample, and 
and 
are the final and initial temperatures respectively. What is the change in entropy when 20 grams of aluminum with a specific heat of 0.900 J/gm K is cooled from 60.0
to 10.0
Many meteorites appear to have formed very early in the solar system's history. How do these meteorites support the nebular theory's scenario for the formation of the terrestrial planets?
A) The appearance and composition of these meteorites is just what we'd expect if metal and rock condensed and accreted as the nebular theory suggests. B) The sizes of these meteorites are just what we'd expect if metal and rock condensed and accreted as the nebular theory suggests. C) The overall composition of these meteorites is just what we believe the composition of the solar nebula to have been: mostly hydrogen and helium. D) The appearance and composition of these meteorites matches what we observe in comets today, suggesting that they were once pieces of icy planetesimals.
What temperature exists inside a solar collector (effective collection area of 15 m2 ) on a bright sunny day when the outside temperature is +20.°C?
Assume that the collector is thermally insulated, that the sun irradiates the collector with a power per unit area of 600 W/m2, and that the collector acts as a perfect black body. A) 107°C B) 154°C C) 93°C D) 73°C E) 33°C
Which of the following intermolecular forces best describes why nonpolar molecules like gasoline (C8H18) have only limited solubility in water?
A) dipole-dipole B) induced dipole-induced dipole C) dipole-induced dipole D) ion-dipole E) Both A and B