# Can a sensor tell the difference between gravity vs. acceleration?

Are the effects of gravity and acceleration identical to the point that no sensor can tell the difference?

• Gravity is a force, which causes object to accelerate towards the centre of the earth. Most sensors can’t intrinsically differentiate between this force and other external forces. But usually, the sensor is held from falling, and as such doesn’t feel the force of gravity Oct 12 '19 at 18:32
• Einstein did not think they were different. Oct 12 '19 at 19:15
• I don't think this qualifies as an answer but I don't have enough reputation to post a comment. The 'acceleration due to gravity' is a set constant (and that's 10 around these parts) but for this case it'd be 9.80665 meters per second squared. If you use an accelerometer then simply checking against that value will give you a good enough idea. There's also the obvious caveat of additional forces. If I throw a ball at the ground gravity doesn't account for the entirety of the balls acceleration and the accelerometer won't know the difference. Oct 12 '19 at 20:44
• Acceleration regarding to what reference system? A position sensor (GPS, laser, inductive, ...) can clearly tell you the acceleration value. A simple acceleration sensor cannot distingush betwee acceleration due to gravity and kinematic acceleration. May 7 '20 at 12:33

2) Push the box downwards with an acceleration of $$9.81m/s^2$$, from an ‘applied force’