What is the correct force exerted by the seat in a pulley and force problem?

In summary, a 612 N person sitting in a 16.0 N seat pulls on a massless rope attached to the seat with a force of 348 N. The problem asks to determine the person's acceleration (1.06 m/s^2) and the force exerted by the seat on the person. The rope also exerts a tension force on the system, resulting in a total force of 330 N in the upward direction.
  • #1
kristen151027
43
0
Here's the question:
A 612 N person is sitting in a 16.0 N seat with one end of a massless rope attached to the seat. The rope runs over an ideal pulley, and the other end of it is in the person's hand. The person pulls the loose end of the rope with a force of 348 N.

The problems asks to determine the acceleration of the person (1.06 m/s^2) and the force that the seat exerts on the person.

I found the force exerted by the seat on the person to be 332 N (348 N - 16.0 N), but that is not the correct answer. What am I missing?
 
Physics news on Phys.org
  • #2
Start by figuring out the acceleration of "seat + person". What forces act on that system? (Hint: What force does the rope exert on that system? How many places does the rope attach?)
 
  • #3
Got it.
The forces exerted on the person are the tension of the rope in the upward direction, the force of the seat in the upward direction, and its weight (mg) in the downward direction. So,

T + F_seat + (-mg) = ma
348 N + F_seat - 612 N = (62.45 kg)(1.06 m/s^2)
F_seat = 330 N

Thanks!
 

1. What is a pulley and how does it work?

A pulley is a simple machine that consists of a wheel with a groove around its circumference and a rope or belt that runs along the groove. When one end of the rope is pulled, the wheel turns and lifts or moves the object attached to the other end of the rope. This allows for the application and transmission of force over a distance, making it easier to lift heavy objects.

2. How does the number of pulleys affect the force required to lift an object?

The number of pulleys affects the force required to lift an object by changing the direction of the force. With each additional pulley, the force required to lift the object is reduced. This is because the weight of the object is distributed among more strands of the rope, making it easier to lift.

3. What is the difference between fixed and movable pulleys?

A fixed pulley is attached to a stationary object, while a movable pulley is attached to the object being lifted. In a fixed pulley, the direction of the force remains the same, but the force required to lift the object is reduced. In a movable pulley, the direction of the force changes, making it easier to lift the object.

4. How can I calculate the mechanical advantage of a pulley system?

The mechanical advantage of a pulley system can be calculated by dividing the load (the weight of the object being lifted) by the effort (the force applied to lift the object). For example, if the load is 100 pounds and the effort is 50 pounds, the mechanical advantage would be 2. This means that the pulley system makes it possible to lift the load with half the force.

5. How do I determine the ideal pulley system for a specific lifting task?

The ideal pulley system for a specific lifting task depends on the weight of the load, the distance it needs to be lifted, and the amount of force that can be applied to lift it. Generally, the more pulleys in the system, the less force is required to lift the load, but the distance the rope needs to be pulled will also increase. It's important to consider these factors to determine the most efficient and safe pulley system for the task at hand.

Similar threads

  • Introductory Physics Homework Help
Replies
9
Views
2K
  • Introductory Physics Homework Help
Replies
6
Views
2K
  • Introductory Physics Homework Help
Replies
2
Views
679
  • Introductory Physics Homework Help
Replies
10
Views
3K
  • Introductory Physics Homework Help
Replies
30
Views
1K
  • Introductory Physics Homework Help
Replies
24
Views
1K
  • Introductory Physics Homework Help
Replies
33
Views
6K
  • Introductory Physics Homework Help
Replies
6
Views
1K
  • Introductory Physics Homework Help
Replies
8
Views
2K
  • Introductory Physics Homework Help
Replies
7
Views
1K
Back
Top