A student pulls a wooden box along a rough horizontal floor at constant speed by means of a force P as shown to the right. Which of the following must be true?
Correct answer: A. P > fand N < W
- A. P > fand N < W
- B. P > f and N = W
- C. P = f and N > W
- D. P = f and N = W
Explanation
The correct answer is that P > f and N < W. The force P is applied at an upward angle, which means it has both horizontal and vertical components. The vertical component of P reduces the normal force, making it less than the weight, W. The horizontal component of P must be greater than the frictional force, f, to maintain constant speed. The other options are incorrect because they either disregard the influence of the vertical component of P or misinterpret the relationship between P, f, and N.
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Displacement, velocity and acceleration describe motion, including the horizontal and vertical components of projectile motion. The chapter connects these quantities with Newton's laws, momentum and impulse, then applies conservation of momentum to collisions, distinguishing elastic collisions from inelastic ones.
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