Find work?!?!?

You drop a 1.60 kg textbook to a friend who stands on the ground 10.0 m below the textbook with outstretched hands 1.5 m above the ground. How much work is done on the textbook by its weight as it drops to your friend's hands?





What is the change in the gravitational potential energy of the textbook-Earth system during the drop?





If the gravitational Potential energy of that system is taken to be zero at ground level, what is its potential energy when the textbook is released?





If the gravitational Potential energy of that system is taken to be zero at ground level, what is its potential energy when the textbook reaches the hands?

Find work?!?!?
a)


Assuming your friend catches it in approximately 0m, the energy required to speed up the textbook must be the same as that required to slow it down again. This is the kinetic energy acquired in the fall, i.e., 10*9.81*1.6 = 156.96J.





b)


Same as in (a).





c)


(10+1.5)*9.81*1.6 = 180.504J.





d)


1.5*1.6*9.81=23.544J.





Basically, all you need to know is that gravitational potential energy (E) = mass * acceleration due to gravity * height, so:





E = mgh





So long, adiós.