A piston-cylinder arrangement, shown in figure, contains air at 250 kPa and 300oC. The 50-kg piston has a diameter of 0.1 m and, initially pushes against the stops. The atmosphere is at 100
kPa and 20oC.
(a) Represent the forces acting on the piston through a free body diagram for initial condition.
The cylinder now cools as heat is transferred from air to the ambient surroundings, thereby
reducing the air pressure, resulting in the piston to start moving down.
(b) Represent the forces acting on the piston through a
free body diagram for this condition.
(c) Find the pressure when the piston is just about to
move down?

When someone eats food

Iwould say earthquakes.

B? i think so but hope that's right and answers your question

The figure is missing but we can answer anyway.the correct answer is "releasing the string". in fact, when the person is holding the bow and the arrow, the kinetic energy of the arrow is still zero (because the arrow is not moving). the moment the arrow is released, it acquires a velocity v, so its kinetic energy will become different from zero: where m is the mass of the arrow and v its velocity.  all the other options, instead, do not increase the kinetic energy of the system: -  pulling farther back on the string : this will just increase the elastic potential energy of the system-  holding the arrow higher: this will increase the gravitational potential energy of the system (which is given by u=mgh, where h is the height above the ground)-  decreasing the mass of the arrow: this will decrease the gravitational potential energy of the system (which is given by u=mgh, where m is the mass)