Answer: 20*sqrt(3) N.
- A 20 N
- B 34.6 N
- C 40 N
- D 20*sqrt(3) N
Correct answer: D. 20*sqrt(3) N
Explanation: N = mg cos(theta) = 4 x 10 x cos30 = 40 x (sqrt(3)/2) = 20*sqrt(3) approximately 34.6 N.
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.