10. You try to move a couch across the floor but it doesn't move. What is the other force acting on the couch?
A. only you
B. inertia
C. static friction (my answer)
D. kinetic friction
11. You finally get the couch in Problem 10 to move. What other force is acting on the couch now?
A. only you
B. inertia
C. static friction
D. kinetic friction (my answer)
Are these correct?
both correct.
For question 10, the correct answer is indeed C. static friction. When you try to move the couch, there is a force called static friction that opposes the relative motion between the couch and the floor. Static friction acts to keep the two surfaces in contact and prevents the couch from sliding.
To determine this, you can analyze the scenario by considering the forces involved. First, there is the force applied by you to move the couch. However, the couch doesn't move, which means there must be an equal and opposite force acting on it. That force is static friction, which is preventing the couch from sliding across the floor.
For question 11, the correct answer is D. kinetic friction. Once the couch starts moving due to your applied force, the force of static friction transitions into the force of kinetic friction. Kinetic friction is the force that opposes the sliding motion of two surfaces in contact.
To determine this, you can observe that once the couch begins to move, the force of static friction can no longer hold it in place. Instead, the force of kinetic friction acts as the resistance to the sliding motion of the couch across the floor.
So, your answer choices for both questions are correct.