Answer - corona, chromosphere, photosphere
Answers:
a) 5400000 J
b) 45.92 m
Explanation:
a) The kinetic energy 
of an object is given by:
Where:
is the mass of the train
is the speed of the train
Solving the equation:
This is the train's kinetic energy at its top speed
b) Now, according to the Conservation of Energy Law, the total initial energy is equal to the total final energy:
Where:
is the train's initial kinetic energy
is the train's initial potential energy
is the train's final kinetic energy
is the train's final potential energy, where 
is the acceleration due gravity and 
is the height.
Rewriting the equation with the given values:
Finding :
Answer:
I'd say C is the answer they want, though my pedantic side wants to argue for B being true as well.
All machines are not 100% efficient because of <span>C. Friction</span>
I think the question meant to say net force on the box. Since force is a vector, the direction matters. 20N left is negated completely by the 50N right, which means the net force is 50N-20N to the right, 30N.
