Answer: 5/11 m/s backward.
- A 0.45 m/s backward
- B 0.5 m/s backward
- C 5/11 m/s backward
- D 5 m/s forward
Correct answer: C. 5/11 m/s backward
Explanation: Man's speed relative to ground = 5 - v<sub>boat</sub>. Momentum conservation: 0 = 50(5 - v<sub>boat</sub>) - 500 v<sub>boat</sub>. 250 = 550 v<sub>boat</sub>. v<sub>boat</sub> = 250/550 = 5/11 m/s backward.
Free-body diagram of a block on an incline: weight (mg) resolves into mg sinθ along the slope and mg cosθ into the slope, balanced by the normal force N and friction f.
Concept context
Newton's three laws, friction, circular motion, and free body diagrams.