NEED HELP ASAP, WILL GIVE BRAINLIEST Which is an example of convection currents?

marshmallows toasting over a campfire
a pot being heated by an electric burner
feet getting hot when stepping across sand
a radiator emitting warm air and drawing in cool air

Two friends are having a conversation. anna says a satellite in orbit is in freefall because the satellite keeps falling toward earth. tom says a satellite in orbit is not in freefall because the acceleration due to gravity is not 9.80 m/2 . who do you agree with and why?

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.

Atruck with 34-in.-diameter wheels is traveling at 55 mi/h. find the angular speed of the wheels in rad/min, *hint convert miles to inches & hours to minutes: