# SAT Subject Physics Practice Question 222: Answer and Explanation

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**Question: 222**

**68.**

A block is attached to the end of a linear spring, the other end of which is anchored to a wall. The block is oscillating between extreme positions X and Y on a frictionless table, and when the block is at Point O, the spring is at its natural length. The value of the spring’s force constant, *k*, is known, but the mass of the block, *m*, is unknown.

Knowing which one of the following would permit you to calculate the value of *m* ?

A. The acceleration of the block at Point O

B. The acceleration of the block at Point Y

C. The speed of the block as it passes through O

D. The distance between X and Y

E. The time required for the block to travel from X to Y

**Correct Answer:** E

**Explanation:**

The frequency of the oscillations, *f*, can be found from the equation *f* = . Since *k* is known, all we need is *f* in order to calculate *m*. If we know the quantity given in E, we can double it to get the period, then take its reciprocal to obtain *f*.