12. Which of the following best explains why an ice skater is able to coast on ice for a long distance without pushing off in a straight line across the ice?
Answer: B
An ice skater can coast on ice for a long distance without pushing off because the force of friction on the blades of the skates is less than the force of friction on the ice.
The ability of an ice skater to glide smoothly over ice is primarily due to the low friction between the skate blades and the ice surface. This minimal friction allows the skater to maintain their momentum over longer distances without the need for continuous pushing.
A) The force of friction on the blades of the skates is greater than the force of friction on the ice.
This option is incorrect because if the friction on the blades were greater than that on the ice, the skater would not be able to glide efficiently. Increased friction would slow the skater down, negating the very reason why they can coast for long distances.
B) The force of friction on the blades of the skates is less than the force of friction on the ice.
This statement accurately describes the situation. The specialized design of ice skates reduces friction between the blades and the ice, allowing skaters to maintain their speed and glide for extended periods. This is the fundamental principle that enables effective coasting on ice.
C) The ice exerts a constant forward force on the skater.
This option is incorrect as there is no constant forward force exerted by the ice. Instead, the skater's motion is governed by their initial kinetic energy, and they rely on the minimal friction to maintain their speed rather than any forward force from the ice.
D) The buoyant force on the blades of the skates is greater than the weight of the skater.
This option is also incorrect. Buoyant force is not a relevant factor in this context since it pertains to fluids and does not apply to the interaction between the skater's blades and the ice surface. The skater's weight and the ice's friction are more significant in explaining their ability to coast.
Conclusion
The correct answer, B, clearly illustrates that the low friction between the skate blades and the ice is what allows skaters to maintain their momentum and glide efficiently. All other options fail to accurately reflect the physics of skating, either misrepresenting the forces at play or introducing irrelevant concepts. Understanding this principle is essential for grasping the mechanics of ice skating and the dynamics involved in coasting.