📚 Topic Summary
Friction is a force that opposes motion between surfaces in contact. Static friction ($f_s$) prevents the initiation of motion, while kinetic friction ($f_k$) opposes motion once it has started. The maximum static friction is given by $f_{s,max} = \mu_s N$, where $\mu_s$ is the coefficient of static friction and $N$ is the normal force. Kinetic friction is given by $f_k = \mu_k N$, where $\mu_k$ is the coefficient of kinetic friction and $\mu_k$ is the coefficient of kinetic friction. Typically, $\mu_s > \mu_k$. This means it takes more force to start an object moving than to keep it moving.
📝 Part A: Vocabulary
Match the term with the correct definition:
| Term |
Definition |
| 1. Static Friction |
A. The force that opposes motion once it has started. |
| 2. Kinetic Friction |
B. The normal force divided by the friction force. |
| 3. Coefficient of Static Friction |
C. The force that opposes the initiation of motion. |
| 4. Coefficient of Kinetic Friction |
D. The ratio of kinetic friction force to the normal force. |
| 5. Normal Force |
E. The perpendicular force exerted by a surface on an object in contact with it. |
Match them up: 1-?, 2-?, 3-?, 4-?, 5-?
✍️ Part B: Fill in the Blanks
Complete the following paragraph using the words: static, kinetic, coefficient, normal, friction.
_______ is a force that opposes motion between surfaces in contact. _______ friction prevents an object from starting to move, while _______ friction acts on an object already in motion. The magnitude of these forces depends on the _______ force and the _______ of friction between the surfaces.
🤔 Part C: Critical Thinking
A wooden block is resting on an inclined plane. Describe the forces acting on the block. What must be true for the block to remain at rest? If the angle of the incline is increased, what happens to the forces, and when will the block start to slide?