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Question 12 of 36

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SAT Subject Test

The figure shows a 5-kilogram block suspended by a cord from the ceiling.

A 5-kilogram block is suspended by a cord from the ceiling, as shown above. The force exerted on the block by the cord is most nearly

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zero

Correct Answer: 
No

25 N

Correct Answer: 
No

50 N

Correct Answer: 
Yes

100 N

Correct Answer: 
No

200 N

Correct Answer: 
No

The correct answer is 50 N. The block is in equilibrium so the vector sum of the forces acting on it must be zero. The force exerted by the cord on the block must therefore be opposite in direction and equal in magnitude to the weight of the block, which is the only other force exerted on it. The weight of the block is equal to m times g, where m is the 5-kilogram mass of the block and g is the acceleration due to gravity at Earth’s surface, which in this test may be approximated as 10 invisible times straight m divided by straight s to the power of 2 end exponent. The product of these two values is 50 newtons, which is also equal to the force exerted by the cord.

Question Difficulty: 
easy