Physics students study a piano being pulled across a room on a rug. They know that when it is at rest, it experiences a gravitational force of 2200 N. When it is being pulled with 1200 N it is sliding across the room in equilibrium, but the students feel like they had to pull harder than 1200 N at first to begin motion.

While the piano slides in equilibrium, the forces balance, so its kinetic friction is 1200 N, equal in size to the pulling force. To start the piano moving, the students must overcome the maximum static friction, which is greater than the kinetic friction. Therefore, the static friction needed to start motion is greater than 1200 N, matching choice C.

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