Spring Constants/Work And Energy

In summary, the conversation is about two physics homework questions related to the concept of work and mechanical energy. The first question involves a mass attached to a spring, while the second question involves a sphere falling through a liquid. The person is seeking help with finding the velocity and work done by the frictional force in each scenario. They have attempted to solve the problems but are struggling and are seeking assistance.
  • #1
eann595
1
0
I'm having a bit of a problem with these homework questions, if anyone could help out that would be great!

1. A 15 kg mass is attached to a massless spring by a light string that passes over a frictionless pulley. The spring has a force constant k= 500 N/m and is unstretched when the mass is relased. What is the velocity when it has fallen a distance of .30 m?

2. A 0.75 kg sphere is dropped through a tall column of liquid. When the sphere has fallen a distance of 2.0 m, it is observed to have a velocity of 2.5 m/s
a. how much work was done by the frictional force exerted on the sphere by the liquid?
b. what is the average force of friction during the displacement of 2.0 m?

I am completely stumped, =( please help!
 
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  • #2
PF usually asks that you show an attempt first.
 
  • #3
In both problems, analyze what happens to the mechanical energy.
 
  • #4
I'm struggling with the same questions as eann595, but I attempted to work them out so please help!:

1.) a 0.75 kg sphere is dropped through a tall column of liquid. When the sphere has fallen a distance of 2.0 m, it is observed to have a velocity of 2.5 m/s.
a.) How much work was done by the frictional force exerted on the sphere by the
liquid?

* I need the net work of friction, so I started with Wnet(Fr) = change in KE = ma.
* Fr x cos(180) x d = 1/2mv^2 = ma.
* Fr x -1 x 2.0m = 1/2(0.75kg)(2.5m/s)^2 = (0.75kg)(a)
* -2.0m x Fr = 2.34 kg x m squared/sec squared = (0.75)(a)

I have a feeling that b/c acceleration is not given, it equals g aka 9.8 m/s^2 (??) Am I on the right track with this problem?

b.) What is the average force of friction during the displacement of 2.0m?

This one I think I need to know the answer to letter a.) to solve.
 

FAQ: Spring Constants/Work And Energy

What is a spring constant and how is it calculated?

A spring constant, also known as the force constant, is a measure of the stiffness of a spring. It represents the amount of force required to stretch or compress a spring by a certain distance. It is calculated by dividing the force applied to the spring by the distance it is stretched or compressed.

How is the work done by a spring calculated?

The work done by a spring is calculated by multiplying the force applied to the spring by the distance it is stretched or compressed. This is known as Hooke's Law, which states that the force applied to a spring is directly proportional to the distance it is stretched or compressed.

What is the relationship between spring constants and work?

The relationship between spring constants and work is that the spring constant determines the amount of force required to stretch or compress a spring, which in turn affects the amount of work done by the spring. A higher spring constant means a stiffer spring and more force is needed to produce the same amount of work.

How does energy relate to spring constants and work?

Energy is directly related to spring constants and work. The work done by a spring is stored as potential energy in the spring, which is represented by the spring constant. The higher the spring constant, the more potential energy is stored in the spring.

Can the spring constant of a material change?

Yes, the spring constant of a material can change. It is affected by factors such as temperature, stress, and material properties. For example, a material may have a higher spring constant at lower temperatures, but as the temperature increases, the spring constant may decrease. Additionally, the spring constant can change if the material is damaged or undergoes plastic deformation.

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