I Need Help with a Spring Problem, Net Forces

In summary, when a box is attached to a wall with a spring and a force is applied to the box, the spring will exert an equal force in the opposite direction. This can be represented by F(push) = 20N and F(spring) = -kd, with F(net) = F(push) - F(spring) resulting in a net force of zero. The negative sign in this equation indicates that the restoring force is in the opposite direction of the displacement. By subtracting a negative, the net force appears to be larger but it is not incorrect. A sketch of the situation can help clarify which direction is considered positive.
  • #1
Jaccobtw
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Homework Statement
Why is there a negative on the spring constant in this equation?: F = -kd
Relevant Equations
F = -kd
Let's say you have a box and there is a spring attached to it and the other end of the spring is attached to the wall. If you press the box towards the wall the spring presses back against the box with an equal force. F(push) = 20N, F(spring) = -kd. F(push) - F(spring) = F(net). Which is zero. However, because there is a negative, and because I am subtracting a negative, you get a much larger positive number of net force. Isn't this incorrect?
 
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  • #2
The negative sign shows that the restoring force is in the opposite direction from the displacement (hence "restoring" force). The negative sign is associated with the displacement, not with the spring constant.

Does that help? :smile:
 
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  • #3
BTW, keep asking good questions! :smile:
 
  • #4
What also helps is a sketch of the situation, showing which way you consider positive...
 
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What is a spring problem?

A spring problem is a physics problem that involves calculating the motion, forces, and energy of a spring system. This usually includes determining the displacement, velocity, acceleration, and net forces acting on the spring.

What are net forces?

Net forces are the sum of all the forces acting on an object. In the context of a spring problem, net forces refer to the total force acting on the spring, which is a combination of the force of the spring itself and any external forces acting on it.

How do I calculate net forces in a spring problem?

To calculate net forces in a spring problem, you need to identify all the forces acting on the spring and their respective magnitudes and directions. Then, you can use the equation Fnet = ma, where Fnet is the net force, m is the mass of the object attached to the spring, and a is the acceleration of the object.

What is the role of gravity in a spring problem?

Gravity is one of the external forces that can act on a spring system, depending on the orientation of the spring. In some cases, gravity can contribute to the net force acting on the spring, and therefore, affect its motion and behavior.

What are some common mistakes when solving spring problems?

Some common mistakes when solving spring problems include not considering all the forces acting on the spring, not correctly identifying the direction and magnitude of forces, and not using the correct equations to solve for the desired variables. It is important to carefully analyze the problem and use the appropriate equations and principles to arrive at the correct solution.

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