Final answer:
To determine if you're accelerating up or down in an elevator, observe the scale reading while holding a 10 N weight. If the reading is greater than 10 N, the elevator is accelerating upwards; if it is less, you're going down. At constant velocity or free-fall the reading would be the actual weight or zero, respectively.
Step-by-step explanation:
Using a scale and a 10 N weight, you could determine if you are accelerating upward or downward in an elevator by observing the scale reading.
- If the elevator accelerates upward, the force required to accelerate the object is greater, and thus, the scale reading will be higher than 10 N.
- If the elevator accelerates downward, the scale will read less than 10 N, because the acceleration is negative. In the case of free-fall, where acceleration due to gravity is the only force acting, the scale would read zero, indicating weightlessness.
At a constant velocity, whether it's upward, downward, or stationary, the acceleration is zero since the change in velocity over time (a = Δv/Δt) is zero.
In this situation, the scale would read the actual weight of the object, which is 10 N, because no additional force is required to change the object's momentum.
Einstein's everyday example shows that these effects are not just sensations, but can be quantitatively measured, which is what you would do with the scale in the elevator. Noticing a change in the scale reading due to acceleration confirms that the elevator and consequently your body, is not in a uniform motion but is instead experiencing a net force.