Tides rise on the sea. why?

A900 kg roller coaster car is travelling westward on the track and begins to slow down from 18m/s to 2m/s. how long does it take the roller coaster car to decelerate if the force acting on the car to slow it is 7024n? how far does the roller coaster travel during this time?

How do you tell if someone actually cares about you? and just say they do?

Asheet of steel 1.5 mm thick has nitrogen atmospheres on both sides at 1200oc and is permitted to achieve a steady-state diffusion condition. the diffusion coefficient for nitrogen in steel at this temperature is 6 x 10- 11 m2 /s, and the diffusion flux is found to be 1.2 x 10-7 kg/m2 -s. also, it is known that the concentration of nitrogen in the steel at the high-pressure surface is 4 kg/m3 . how far into the sheet from this high-pressure side will the concentration be 2.0 kg/m3 ? assume a linear concentration profile.