**AP Physics 1 Question 103: Answer and Explanation**

### Test Information

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**Question: 103**

**3.** Spring scales are used to measure the net force applied to an object; a sonic motion detector is used to measure the object’s resulting acceleration. A graph is constructed with the net force on the vertical axis and the acceleration on the horizontal axis. Which of the following quantities is directly measured using the slope of this graph?

- A. Gravitational mass
- B. Weight
- C. Velocity
- D. Inertial mass

**Correct Answer:** D

**Explanation:**

**D**-The relevant equation connecting force and mass is *F* = *ma*. The slope is the vertical axis divided by the horizontal axis, or *F/a* = *m*. So the slope is mass-but why inertial not gravitational mass? Inertia is defined as an object's resistance to acceleration. If acceleration is involved, you're talking inertial mass. Gravitational mass would involve the weight of an object in a gravitational field.