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Writer's picturekeshprad

CollegeBoard SAT Physics Study Guide PT1 Q24


24) In this question, we are told that the block is pulled over a rough surface by a constant tension force. Now, we want to validate the statements in the answer choices. However, the object is traveling at a constant velocity, which means there is no acceleration. Let’s start with a free-body diagram of all the forces.

Where T is the tension force and f is the frictional force

Remember, since the object is pulled across a rough surface, friction is at work. The tension and the friction are pulling in opposite directions along the x-axis, so we can subtract them to find our net force.

Where F is net force, T is tension force, and f is frictional force

Looking back at the problem, it is crucial to note that the problem mentions the block moves with a constant velocity. This means the net acceleration produces by the sum of the forces is 0.

Where F is net force, m is mass, a is acceleration, T is tension force, and f is frictional force

Now we have proven that the tension force and friction force are equal in magnitude but point in different directions (demonstrated in our free-body diagram of forces) Our answer must be choice C, which explains just this.


Answer: C

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