A 75-kg man stands on a spring scale in an elevator.  During the first 3 seconds of motion from rest, the tension T in the hoisting cable is 8300 N.  Find the reading R of the scale in newtons during this interval and the upward velocity v of the elevator at the end of the 3 seconds.  The total mass of the elevator, man, and scale is 750 kg.

Elements Of Electromagnetics
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A 75-kg man stands on a spring scale in an elevator.  During the first 3 seconds of motion from rest, the tension T in the hoisting cable is 8300 N.  Find the reading R of the scale in newtons during this interval and the upward velocity v of the elevator at the end of the 3 seconds.  The total mass of the elevator, man, and scale is 750 kg.

### Elevator and Passenger Forces Diagram

This diagram illustrates the forces acting on an elevator and a passenger standing inside it.

#### Components:

1. **Elevator System:**
   - The elevator is depicted as a rectangular box containing a standing passenger.
   - **Forces Acting on the Elevator:**
     - **Tension (T):** An upward force of 8300 N is acting on the elevator.
     - **Weight of the Elevator:** The weight acting downward is calculated as \(750 \times 9.81 = 7360 \, \text{N}\).
     - **Acceleration (\(a_y\)):** Indicates the direction of net acceleration acting upwards.

2. **Passenger:**
   - Illustrated as a figure standing on a platform, representative of the elevator floor.
   - **Forces Acting on the Passenger:**
     - **Normal Reaction (R):** An upward reaction force supporting the passenger.
     - **Weight of the Passenger:** The weight is calculated as \(75 \times 9.81 = 736 \, \text{N}\).
     - **Acceleration (\(a_y\)):** Points upward, indicating the acceleration affecting the passenger.

#### Explanation:

- **Tension vs. Weight (Elevator):** The tension in the cable (\(T = 8300 \, \text{N}\)) is greater than the weight of the elevator (\(7360 \, \text{N}\)), suggesting an upward acceleration.
- **Net Force on Passenger:** The normal reaction \(R\) ensures the passenger remains stationary relative to the elevator when considering the net effect of gravity and motion.
- **Acceleration of System:** The upward-directed arrows labeled \(a_y\) indicate that both the elevator and passenger experience a net acceleration upward, which affects the normal forces and the sensation of weight.

This diagram is useful for understanding the interplay of forces in a system subject to gravitational and mechanical forces, such as an elevator in motion.
Transcribed Image Text:### Elevator and Passenger Forces Diagram This diagram illustrates the forces acting on an elevator and a passenger standing inside it. #### Components: 1. **Elevator System:** - The elevator is depicted as a rectangular box containing a standing passenger. - **Forces Acting on the Elevator:** - **Tension (T):** An upward force of 8300 N is acting on the elevator. - **Weight of the Elevator:** The weight acting downward is calculated as \(750 \times 9.81 = 7360 \, \text{N}\). - **Acceleration (\(a_y\)):** Indicates the direction of net acceleration acting upwards. 2. **Passenger:** - Illustrated as a figure standing on a platform, representative of the elevator floor. - **Forces Acting on the Passenger:** - **Normal Reaction (R):** An upward reaction force supporting the passenger. - **Weight of the Passenger:** The weight is calculated as \(75 \times 9.81 = 736 \, \text{N}\). - **Acceleration (\(a_y\)):** Points upward, indicating the acceleration affecting the passenger. #### Explanation: - **Tension vs. Weight (Elevator):** The tension in the cable (\(T = 8300 \, \text{N}\)) is greater than the weight of the elevator (\(7360 \, \text{N}\)), suggesting an upward acceleration. - **Net Force on Passenger:** The normal reaction \(R\) ensures the passenger remains stationary relative to the elevator when considering the net effect of gravity and motion. - **Acceleration of System:** The upward-directed arrows labeled \(a_y\) indicate that both the elevator and passenger experience a net acceleration upward, which affects the normal forces and the sensation of weight. This diagram is useful for understanding the interplay of forces in a system subject to gravitational and mechanical forces, such as an elevator in motion.
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