Explain why do we feel that our weight is decreased in a lift descending with uniform acceleration.

Understanding Newton's Second Law of Motion is crucial when explaining why our perceived weight changes in a descending lift. This law states that the force (\( F \)) acting on an object is the product of its mass (\( m \)) and acceleration (\( a \)): \[ F = m \times a \] But what does this mean for us in a lift? Well, when the lift is descending with acceleration, it's as if our body experiences an additional force that opposes our weight. This is why we feel lighter. Our actual weight force, due to gravity, remains the same, but the 'felt' force—the reaction force from the lift floor, known as the normal force—decreases, altering our sensation of weight. In summarizing, Newton's Second Law helps us understand that the interaction between mass, acceleration, and force is what leads to this change in weight perception.

Riding in a lift involves more forces than we might initially notice. When stationary, we're subject to gravity pulling us down, and the lift's floor pushing back up with equivalent force. This upward force is the normal force. During a descent with uniform acceleration, two main forces are at play: the gravitational force (our weight) and the normal force. As the lift accelerates downward, it slightly reduces the normal force felt by us. This reduction causes the sensation of being lighter. To fully grasp the scenario, it's important to remember that both gravity and lift acceleration contribute to the overall forces we experience inside the lift.

The normal force is the support force exerted upon an object that is in contact with another stable object. For instance, if you're standing in a lift, the floor exerts an upward normal force that balances your weight under normal conditions. However, in a descending lift, this force changes.
Suppose the lift is descending with uniform acceleration, the normal force becomes less than your actual weight. This is because the lift's floor is moving downward, reducing the force it needs to exert to support you. The normal force, then, doesn't just represent the 'push back' from the lift floor—it's our tactile connection to gravity and acceleration, it's what we 'feel' as our weight.

Uniform acceleration refers to a constant change in velocity. When a lift is moving downward with uniform acceleration, it's smoothly increasing its speed at a steady rate downwards, which can affect our perception of weight.

According to physics, the only difference between being at rest on the ground and moving down with uniform acceleration should be in the forces we feel, not in the actual weight—because weight as a measure of gravitational force doesn't change. But our perception is different due to the altered normal force, and that's where the interesting bit about uniform acceleration comes into play—it tweaks our sensation of weight without altering the gravitational pull on our body.