Superman stops a "speeding locomotive" of mass 8.0x103 kg in 4.0 seconds. If the train was originally moving at 40.m/s, a) what is the change in momentum?

b.) What is the magnitude of the force which Superman exerts on the train?

Given the position vector of the particle r(t)=(t+1)i+(t^2−1)j+2t k, find the particle's velocity and acceleration vectors at t=1

Utah's great salt lake has an average salinity seven times higher than that of the oceans. very few multicellular organisms live in this harsh environment. an example is the brine shrimp, which must devote a large portion of its metabolic energy to osmoregulation. these brine shrimp must available hint(s)utah's great salt lake has an average salinity seven times higher than that of the oceans. very few multicellular organisms live in this harsh environment. an example is the brine shrimp, which must devote a large portion of its metabolic energy to osmoregulation. these brine shrimp must pump water back into their cells to counter its loss due to osmosisactively pump water back out of their cells to counter its inflow due to osmosissynthesize membranes that are impermeable to substances that upset osmotic balanceactively pump salt back out of their cells to counter its inflow due to osmosis

Why should seat belts not be mandatory quick plz