AP Physics 1hardmcq1 pt
A 10 kg box sits on a surface with μs = 0.4 and μk = 0.3. What is the friction force when a horizontal force of 25 N is applied?
A.30 N
B.25 N
C.0 N
D.40 N
Explanation
Core Concept
Maximum static friction = μs·N = 0.4(10)(9.8) = 39.2 N. Since the applied force (25 N) is less than the maximum static friction, the box doesn't move. The static friction equals the applied force: 25 N.
Correct Answer
B25 N
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