After a hockey player gives a puck a quick ‘hit’ with his stick, the puck slides across the ice at a speed that is essentially constant. A student in a previous class offered the following force diagram and explanation for why the speed of the puck is constant after the hit. What is your evaluation of this explanation?

After a hockey player gives a puck a quick ‘hit’ with his stick, the puck slides across the ice at a speed that is essentially constant. A student in a previous class offered the following force diagram and explanation for why the speed of the puck is constant after the hit.
What is your evaluation of this explanation?
“The initial hit exerts a force on the puck, making the forces acting on the puck unbalanced, and so it starts to move. After the hit ends there is no net force acting on the puck, and when the net force acting on an object is zero, its speed does not change. So after the stick has lost contact with the puck, its speed remains constant.”
Select one:
a. Both the force diagram and the narrative are problematic.
b. The force diagram is problematic but the narrative is accurate.
c. Both the force diagram and the narrative are accurate.
d. The force diagram is accurate but the narrative is problematic.
Frank and Hector are moving two boxes across a rough floor. Frank pushes a 20 kg box with a force of 85 N while a frictional force of 75 N acts on it in the opposite direction. Meanwhile, Hector pushes on the 30 kg box with a force of 105 N while a frictional force of unknown strength acts on it.
Frank and Hector find that as their boxes are moving, they remain side-by-side, so they realize they must both be changing speed at the same rate. What is the strength of the frictional force acting on the 30 kg box?
Select one:
a. 90 N
b. 95 N
c. 75 N
d. 93 N
When shopping for a new car, a professor was surprised to learn that a certain small compact car (mass=800 kg) will speed up (accelerate) at a faster rate than a large SUV (mass=2200 kg), although the SUV has the more powerful engine.
What is the reason that the compact car can speed up at a faster rate than the SUV, despite having a less powerful engine?
Select one:
a. The quantity pushing force / mass is greater for the compact car.
b. The quantity pushing force / mass is smaller for the compact car.
c. The quantity pushing force * mass is smaller for the compact car.
d. The quantity pushing force * mass is greater for the compact car.