# SAT Subject Physics Practice Question 61: Answer and Explanation

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**Question: 61**

**8.** A student is performing a lab experiment on simple harmonic motion. She has two different springs (with force constants *k*_{1} and *k*_{2}) and two different blocks (of masses *m*_{1} and *m*_{2}). If *k*_{1} = 2*k*_{2} and *m*_{1} = 2*m*_{2}, which of the following combinations would give the student the spring–block simple harmonic oscillator with the shortest period?

A. The spring with force constant *k*_{1} and the block of mass *m*_{1}

B. The spring with force constant *k*_{1} and the block of mass *m*_{2}

C. The spring with force constant *k*_{2} and the block of mass *m*_{1}

D. The spring with force constant *k*_{2} and the block of mass *m*_{2}

E. All the combinations above would give the same period.

**Correct Answer:** B

**Explanation:**

The period of the spring-block simple harmonic oscillator is given by the equation *T* = . So, to make *T* as small as possible, we want *m* to be as small as possible and *k* to be as large as possible. Since *m*_{2} is the smaller mass and *k*_{1} is the larger spring constant, this combination will give the oscillator the shortest period.