A crate is pulled across a horizontal floor at constant speed by a rope that makes a…
PHYSICS · Single correct · AP · Physics 1: Algebra-based · Force and Translational Dynamics · Force and Translational Dynamics
Problem
A 10kg crate is pulled across a horizontal floor at constant speed by a rope that makes a 30∘ angle above the horizontal. The rope’s tension is 60N. A student draws the following forces on the crate: weight 98N downward, normal force 98N upward, friction force 20N opposite the motion, and the tension force of 60N along the rope. The student claims the diagram shows the crate in translational equilibrium. Which of the following best evaluates the student’s claim?
(a) The diagram is correct; the forces balance in both horizontal and vertical directions.
(b) The diagram is incorrect; to maintain constant speed, the friction force must be about 60N, not 20N.
(c) The diagram is incorrect because the normal force should be less than 98N when the rope pulls upward.
(d) The diagram is incorrect; the weight of the crate is effectively reduced by the upward pull, so it should be less than 98N.