# Energy Problem with Spring, Gravity, and Friction

• FettuccineAlfredo
In summary, an elevator with a mass of 3000kg is traveling at 30 m/s when it touches a cushioning spring. The safety clamps engage and provide 20,000N of frictional force. The spring constant is 15000 N/m. After the spring compresses 0.8m, the elevator will be traveling at a speed of 30.03 m/s. The work done by friction and the distance traveled by the elevator are both negative.
FettuccineAlfredo

## Homework Statement

An elevator is traveling at 30 m/s just as it touches a cushioning spring. The safety clamps engage at that moment and provide 20,000N of frictional force. The mass of the elevator is 3000kg and the spring constant is 15000 N/m. How fast will the elevator be traveling after the spring compresses 0.8m ?

## Homework Equations

K1+Wf = Ug2+Us2+K2
Allow the point that the elevator touches the spring to be y=0

## The Attempt at a Solution

1/2*m(v1)2+Ffd=mgy2+1/2*kx2+1/2*mv22
Manipulating this around and plugging in numbers gives an answer of 30.03 m/s for me. Am I missing something here?
Edit: d is just the distance along which friction occurs, -.8 m?
x is the compression of the spring, also .8m
y2 is the distance traveled by the elevator, so -.8m

Last edited:
Hi FettuccineAlfredo,

Welcome to Physics Forums!

Can you define your variables used in the attempt at solution? For example, what distinguishes ##d##, ##x##, and ##y_2##?

I didn't check your calculation, but realize that the work done by friction is negative. (As will be y2.)

## 1. What is the energy problem with spring, gravity, and friction?

The energy problem with spring, gravity, and friction refers to the difficulty in accurately calculating the total energy of a system that involves these three forces. This is because each of these forces can either add or remove energy from the system, making it challenging to determine the overall energy balance.

## 2. How do spring, gravity, and friction affect the energy of a system?

Spring, gravity, and friction are all non-conservative forces, meaning they can either add or remove energy from a system. The spring force can add elastic potential energy, gravity can add gravitational potential energy, and friction can remove kinetic energy from the system.

## 3. How can the energy problem with spring, gravity, and friction be solved?

The energy problem with spring, gravity, and friction can be solved by using the principle of energy conservation. This states that the total energy of a system must remain constant, and any changes in one form of energy must be balanced by equal changes in another form of energy.

## 4. How does the coefficient of friction affect the energy problem?

The coefficient of friction plays a significant role in the energy problem with spring, gravity, and friction. A higher coefficient of friction means more energy will be lost due to friction, while a lower coefficient of friction means less energy will be lost. This must be taken into account when solving the energy problem.

## 5. What are some real-life examples of the energy problem with spring, gravity, and friction?

Some real-life examples of the energy problem with spring, gravity, and friction include a pendulum swinging back and forth (gravity and friction), a car's suspension system (spring and friction), and a person jumping on a trampoline (spring and gravity). In each of these examples, the energy of the system is constantly changing due to the interaction of these forces.

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