Lecture on Normal Force in Elevator Scenarios

Introduction

• Focus on how the normal force varies in different elevator scenarios.
• Inspired by personal experience with elevators.
• Consider four scenarios happening in sequence.

Scenario Descriptions

Stationary Elevator

• Velocity: 0 m/s (elevator is not moving).
• Acceleration: 0 m/s².

Elevator Accelerating Upward

• Initial Condition: Press button, elevator starts moving upwards.
• Acceleration: 2 m/s² upward.
• Duration: 1 second.

Constant Velocity Upward

• Condition: After accelerating, the elevator moves at constant velocity.
• Velocity: 2 m/s upward.
• Acceleration: 0 m/s².
• Duration: 10 seconds.

Elevator Decelerating

• Condition: Approaching the desired floor, elevator slows down.
• Acceleration: -2 m/s² (downward).

Calculating Normal Force

• Assume operation near Earth’s surface with gravitational force.
• Example Mass: 10 kg (representing a toddler).
• Gravitational Force: Weight = mass * gravity = 10 kg * 9.8 m/s² = 98 N downward.

Stationary Elevator

• Net Force: 0 N (no acceleration).
• Normal Force: Balances gravitational force = 98 N upward (j direction).

Accelerating Elevator

• Net Force: 20 N upward (2 m/s² * 10 kg).
• Normal Force: Compensates for gravitational force + net force = 118 N upward.

Constant Velocity

• Net Force: 0 N (constant velocity, no net acceleration).
• Normal Force: Same as stationary = 98 N upward.

Decelerating Elevator

• Net Force: -20 N (negative acceleration).
• Normal Force: Less than gravitational force, 78 N upward.

Conclusion

• During acceleration, normal force increases (feel heavier).
• During deceleration, normal force decreases (feel lighter).
• At constant velocity or stationary, normal force equals the gravitational force.
• Important to understand how body perceives these changes.
• Reflect on these concepts during real-world elevator experiences.