12. suppose a person uses a mechanical iack to lift half the weight of a car with a
mass of 1200 kg. during each stroke of the jack handle, the person's hand is
pushing for a distance of 40.0 cm but the car is lifted only 5.0 mm. a)
assuming the jack is 100% efficient. how much force must the person exen
on the handle as the car is lifted? (b) if the actual amount of force required on
the handle is 90.0 n, what is the actual efficiency of the jack?

Global warming will produce rising sea levels partly due to melting ice caps but also due to the expansion of water as average ocean temperatures rise. to get some idea of the size of this effect, calculate the change in length (in m) of a column of water 1.45 km high for a temperature increase of 1.12°c. assume the column is not free to expand sideways. as a model of the ocean, that is a reasonable approximation, as only parts of the ocean very close to