All of the following are kinds of forces except

Acceleration is not a type of force

Acceleration is defined as the rate of change of velocity. It is not a force. Acceleration is actually produced when a force acts upon a body therefore it is the result after we apply any force.

work: w = fd (given)

work done by chet   =50*1 = 50 j

work done by mika =40*2 = 80 j

work done by sara =30*1.5 = 45 j

work done by bill =60*0.5 = 30 j

students in order from the greatest amount of work done to the least is mika> chet> sara> bill

hence option (b) is correct.

i am pretty sure it is c because when people are closer together, they cannot move as freely. picture being in a mostly full elevator, for instance. the people are right next to you, and you can barely move.