How much power is required for a 60 kg student to walk up 40 m of stairs in 90 seconds?

The energy that the student shoud use in order to climb the stairs is equal to its increase in gravitational potential energy:

where m is the mass of the student, g the gravitational acceleration and  the variation of height. Plugging numbers into the equation, we find


The power required for the student to climb the stairs is equal to the work done divided by the time taken:

The answer is b.the gaseous state is electrically positive, while the plasma state is electrically negative.