Calculating Normal Force on a Box with Pulley System | Force Problem Explained

  • Thread starter rachellehowe
  • Start date
  • Tags
    Force
In summary: N = 144.04 N - 3.5 N = 140.54 NFor part b), the weight of the person, 80 kg, adds another downward force of (80 kg)(9.8 m/s/s) = 784 N. So the total weight is now (14.8 kg + 80 kg)(9.8 m/s/s) - 3.5 N = 94.8 kg(9.8 m/s/s) - 3.5 N = 928.08 N - 3.5 N = 924.58 N. Since the box is still in
  • #1
rachellehowe
2
0

Homework Statement


A 14.8kg box is placed on a table, and a rope, rigged to a pulley, is attached to the top of the box. Using the rope, 3.5 Newtons of force, in the upward direction (ie the rope is pulling the box up), is applied to the box.
a)what would be the normal force exerted on the box by the table?

b) if and 80 kg person sat on the box, and there was no longer a force being exerpted by the rope, what would the new normal force on the box be?


Homework Equations





The Attempt at a Solution



I tried for part a). but I'm not sure if I did it right.
F(normal)= mass*gravity
so i just multiplied 14.8kg by 9.8 m/s/s and got 145.04 Newtons then subtracted the amount from the rope and got 145.04-3.5=141.54Newtons but i don't think its right.. i need help!
 
Physics news on Phys.org
  • #2
rachellehowe said:
I tried for part a). but I'm not sure if I did it right.
F(normal)= mass*gravity
so i just multiplied 14.8kg by 9.8 m/s/s and got 145.04 Newtons then subtracted the amount from the rope and got 145.04-3.5=141.54Newtons but i don't think its right.. i need help!
Sounds good to me (assuming I understand the setup).

Here's a better way to think of this problem. Account for all the forces on the box:
(1) the weight, mg, acting down
(2) the rope tension, 3.5 N, acting up
(3) the normal force from the table, Fn, acting up

These forces must add to zero, since the box is in equilibrium:
Fn + 3.5 - mg = 0

So Fn = mg - 3.5
 

1. What is a force?

A force is a push or pull that can change the motion or shape of an object. It is a vector quantity, meaning it has both magnitude and direction.

2. What are the different types of forces?

There are four fundamental forces in nature: gravity, electromagnetism, strong nuclear force, and weak nuclear force. In everyday situations, we commonly encounter forces such as friction, tension, and normal force.

3. How is force measured?

The SI unit for force is the Newton (N), named after the famous scientist Isaac Newton. One Newton is equal to the force required to accelerate a mass of one kilogram by one meter per second squared (1 N = 1 kg * m/s²).

4. What is Newton's First Law of Motion?

Newton's First Law, also known as the Law of Inertia, states that an object will remain at rest or in uniform motion in a straight line unless acted upon by an external force.

5. How do you solve force problems?

To solve a force problem, you can use Newton's Second Law, which states that the net force acting on an object is equal to the product of its mass and acceleration (ΣF = m * a). You can also use vector addition to find the resultant force when multiple forces are acting on an object.

Similar threads

  • Introductory Physics Homework Help
Replies
5
Views
1K
  • Introductory Physics Homework Help
Replies
7
Views
264
  • Introductory Physics Homework Help
Replies
5
Views
2K
  • Introductory Physics Homework Help
Replies
2
Views
2K
  • Introductory Physics Homework Help
Replies
4
Views
1K
  • Introductory Physics Homework Help
Replies
1
Views
828
  • Introductory Physics Homework Help
Replies
12
Views
1K
  • Introductory Physics Homework Help
Replies
2
Views
5K
  • Introductory Physics Homework Help
Replies
6
Views
1K
  • Introductory Physics Homework Help
Replies
30
Views
7K
Back
Top