do not disintegrate due to the nuclear forces. Applications in real life In an elevator either stationary or moving at constant velocity, the normal force on the person's feet balances the person's weight. In an elevator that is accelerating upward, the normal force is greater than the person's ground weight and so the person's perceived weight increases (making the person feel heavier). In an elevator that is accelerating downward, the normal force is less than the person's ground weight and so a passenger's perceived weight decreases. If a passenger were to stand on a weighing scale, such as a conventional bathroom scale, while riding the elevator, the scale will be reading the normal force it delivers to the passenger's feet, and will be different than the person's ground weight if the elevator cab is accelerating up or down. The weighing scale measures normal force (which varies as the elevator cab accelerates), not gravitational force (which does not vary as the cab accelerates). When we define upward to be the positive direction, constructing Newton's second law and solving for the normal force on a passenger yields the following equation: In a gravitron amusement ride, the static friction caused by and perpendicular to the normal force acting on the passengers against the walls results in suspension of the passengers above the floor as the ride rotates. In such a scenario, the walls of the ride apply normal force to the passengers in the direction of the center, which is a result of the centripetal force applied to the passengers as the ride rotates. As a result of the normal force experienced by the passengers, the static friction between the passengers and the walls of the ride counteracts the pull of gravity on the passengers, resulting in suspension above ground of the passengers throughout the duration of the ride. When we define the center of the ride to be the positive direction, solving for the normal force on a passenger that is suspended above ground yields the following equation: where is the normal force on the passenger, is the mass of the passenger, is the tangential velocity of the passenger and is the distance of the passenger from the center of the ride. With the normal force known, we can solve for the static coefficient of friction needed to maintain a net force of zero in the vertical direction: where is the static