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.
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
7th Edition
ISBN:9780190698614
Author:Sadiku, Matthew N. O.
Publisher:Sadiku, Matthew N. O.
ChapterMA: Math Assessment
Section: Chapter Questions
Problem 1.1MA
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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.

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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