John is carrying a shovelful of snow. the center of mass of the 3.00 kg of snow he is holding is 15.0 cm from the
end of the shovel. he is pushing down on the opposite end of the shovel with one hand and holding it up 30.0 cm
from that end with his other hand. ignore the mass of the shovel. sarah says that his hand pushing down on the
shovel must be exerting a greater force than the hand pushing up. james says it is just the reverse. which one, if
either, is correct?
a) sarah, because the hand pushing down must exert a greater force to match the torque
exerted by the snow.
b) james, because, depending on the location of the axis of rotation, the hand pushing down
can counteract the torque exerted by the snow.
c) james, because the hand pushing up must exert a force that equals the sum of the force of
the hand pushing down and the weight of the snow.
d) james, because both (b) and (c) above are correct.
e) neither, because the hands exert forces of equal magnitudes.

What if? physicists often measure the momentum of subatomic particles moving near the speed of light in units of mev/c, where c is the speed of light, and 1 mev = 1.6 ✕ 10−13 kg · m2/s2. based on this, what are the units of momentum for a high-speed subatomic particle in terms of fundamental si units?

An internally reversible refrigerator has a modified coefficient of performance accounting for realistic heat transfer processes of where qin is the refrigerator cooling rate, qout is the heat rejection rate, and is the power input. show that copm can be expressed in terms of the reservoir temperatures tc and th, the cold and hot thermal resistances rt,c and rt,h, and qin, as where rtot rt,c rt,h. also, show that the power input may be expressed as 1.39 a household refrigerator operates with cold- and hot-temperature reservoirs of tc 5 c and th 25 c, respectively. when new, the cold and hot side resistances are rc,n 0.05 k/w and rh,n 0.04 k/w, respectively. over time, dust accumulates on the refrigerator’s condenser coil, which is located behind the refrigerator, increasing the hot side resistance to rh,d 0.1 k/w. it is desired to have a refrigerator cooling rate of qin 750 w. using the results of problem 1.38, determine the modified coefficient of performance and the required power input w under (a) clean and (b) dusty coil conditions. internally reversible refrigerator qout qin w high-temperature reservoir low-temperature reservoir th th,i tc,i tc high-temperature side resistance low-temperature side resistance w qin th tc qinrtot tc qinrtot copm tc qinrtot th tc

Which governments provide garbage collection services to homes and businesses