When a board with a box on it is slowly tilted to larger and larger angle, common experience shows that the box will at some point "break loose" and start to accelerate down the board. The box begins to slide once the component of gravity acting parallel to the boardequals the force of static friction. Which of the following is the most general explanation for why the box accelerates down the board?(A) The force of kinetic friction is smaller than that of static friction, but Fg remains the same.(B) Once the box is moving, Fg is smaller than the force of static friction but larger than the force of kinetic friction.(C) Once the box is moving, Fg is larger than the force of static friction.(D) When the box is stationary, Fg equals the force of static friction, but once the box starts moving, the sliding reduces the normal force, which in turn reduces the friction.

Correct option is A -  The force of kinetic friction is smaller than that of static friction, but Fg remains the same.

Explanation:

(A) The force of kinetic friction is smaller than that of static friction, but Fg remains the same

so easy. just google the electromagnetic waves and it’ll pop up.

note: the given question is incomplete.

complete question is given below.

which is an example of kinetic energy?

a. the energy stored in ethanol  

b. a hockey puck sliding across the ice  

c. a compressed spring  

d. a ball sitting at the top of a ramp

solution: the kinetic energy is the energy posses by the virtue of the motion of the object.

in the given options, a, c and d are the example of potential energy because it is the energy posses by the virtue of the rest of the object. but option b has the kinetic energy as the object is in motion.

hence, a hockey puck sliding across the ice   is the apex example of kinetic energy.

so, the option (b) a hockey puck sliding across the ice   is the correct option.