Ahockey puck is set in motion across a frozen pond. if ice friction and air resistance are neglected, the force
required to keep the puck sliding at constant velocity is
a) the weight of the puck divided by the mass of the puck.
b) the mass of the puck multiplied by 9.8 meters per second per second.
c) qual to the weight of the puck.
d) zero newtons.
e) none of these.

D) Zero newtons

Explanation:

According to the First Newton Law:

"An object keeps its state of rest or its state of uniform motion at constant velocity, when the net force acting on the object is zero"

In this problem, the hockey puck is initially set in motion. While in motion, there are no ice friction and air resistance acting on it: this means that the net force acting on it is zero, so there is no need for an additional force to keep the puck in its state of uniform motion at constant velocity, according to the abovementioned law.

Therefore, the correct answer is

D) zero newtons

answer and explanation;

the duration of a photographic flash is related to an rc time constant, which is 0.100 μs for a certain camera.