Amachine is classified as a compound machine if it

a. has moving parts
b. has an ima greater than 1
c. is made up of two or more simple machines that operate together
d. is very efficient

Aboxcar traveling at 12 m/s approaches a string of 5 identical boxcars sitting stationary on the track. the moving boxcar collides and links with the stationary cars and they all move off together along the track. what is the final speed of the cars immediately after the collision? (you may take the mass of each boxcar to be 18,537 kg.)

Cells in the nervous system have a potential difference of 70 mv across the cell membrane separating the interior of the cell from the extracellular fluid. this potential difference is maintained by ion pumps that move charged ions across the membrane. is this an emf? select the correct answer and explanation. 1)no. the ion pumps cannot separate charges; thus, they cannot create a potential difference. 2)yes. the ion pumps cannot separate charges, but they still can create a potential difference. 3)yes. the ion pumps can actively separate charge; thus, they can create a potential difference. 4)no. the ion pumps can separate charges, but they cannot create a potential difference.

Atemperature inversion can cause a warm air mass to move over a colder air mass. this traps the colder air mass and prevents surface air from rising. this may result in which of these? a) smog b) acid rain c) freezing rain d) a thunderstorm