Which of the following objects provides an inertial frame of reference?

• A. A spacecraft drifting far from any massive body in deep space with its engines off
• B. An elevator moving upward with increasing speed
• C. A spinning merry-go-round in a playground
• D. A car accelerating along a straight road

Answer: (A)

Verified step by step guidance

1. Understand the definition of an inertial frame of reference: it is a frame of reference in which Newton's first law (an object at rest or moving at constant velocity remains so unless acted upon by a net external force) holds true. In other words, it is either at rest or moving with constant velocity (no acceleration).
2. Analyze each option to determine if the frame is accelerating or not. An elevator moving upward with increasing speed is accelerating, so it is not an inertial frame.
3. A spinning merry-go-round is rotating, which means it is undergoing centripetal acceleration, so it is not an inertial frame.
4. A car accelerating along a straight road is clearly accelerating, so it is not an inertial frame.
5. A spacecraft drifting far from any massive body in deep space with its engines off is moving at a constant velocity (no acceleration) and is not influenced by external forces, so it provides an inertial frame of reference.