# Kinetic and Potential Energy Problem Solving

• Callen9
In summary, the conversation revolves around three questions related to kinetic energy and potential energy. The first question involves calculating the angle made by a string with the vertical when the height is 0.1m and the length of the string is 1m. The second question asks for the tension on the string when the mass attached to it is 0.06kg and the height is 0.1m. The third question deals with determining the tension of the string when the mass falls back to its original position from a height of 0.1m. The conversation also includes discussions about using the equations mgh=1/2mv^2 and Net Force=ma to solve the questions.
Callen9

## Homework Statement

Doing some homework with kinetic energy and potential energy. I came across 3 questions that I am struggling with. Basically we have a mass attached to the end of a string. The string is hanging straight down to start off these questions. The following questions assume that the string never has slack in it!

#1, If the length of the string is 1m, calculate the angle made by the string with the vertical when height=.1m?

#2, If the mass is .06kg, what is the tension on the string when height=.1m?

#3, What is the tension of the string when the ball falls back to its original position from a height .1m?

## Homework Equations

Well, I know mgh=1/2mv2, the m will cancel out leaving us with, gh=1/2v2

## The Attempt at a Solution

For #1, If I draw this out, we will have a shape that looks like a right triangle with the hypotenuse of 1m and the vertical side of 1m-height (.1)=.9m. Using SOHCAHTOA we should get an angle of 25.84 degrees.

For #2, I'm not sure about this one, I think I have to label all the forces acting on the mass and do something from there.

For #3,Shouldn't the tension of the string be the Net Force=ma? The only tension acting on the string in the initial position (which is at 0 degrees) should be just the .6kgx9.8?

For #1, If I draw this out, we will have a shape that looks like a right triangle with the hypotenuse of 1m and the vertical side of 1m-height (.1)=.9m. Using SOHCAHTOA we should get an angle of 25.84 degrees.

Yup.

For #2, I'm not sure about this one, I think I have to label all the forces acting on the mass and do something from there.

I'm not sure either. If the mass is moving at h=0.1 m, the tension will be higher, because it has to provide the required amount of centripetal acceleration. However, I think the question assumes that the mass starts off at this position, so it isn't moving at this time.

For #3,Shouldn't the tension of the string be the Net Force=ma? The only tension acting on the string in the initial position (which is at 0 degrees) should be just the .6kgx9.8?

Tension also has to provide the centripetal acceleration, so it's going to be more than 0.6kg*9.8 m/s^2.

So I'm guessing for #2, It would be something along the lines of T1+T2=?... most likely the value of centripetal force.

Same for #3 I guess too.

## 1. What is kinetic energy?

Kinetic energy is the energy an object possesses due to its motion. It is directly proportional to an object's mass and velocity, meaning that the greater the mass and speed, the greater the kinetic energy.

## 2. What is potential energy?

Potential energy is the energy an object possesses due to its position or configuration. It can be further divided into gravitational potential energy, which depends on an object's height and mass, and elastic potential energy, which depends on an object's deformation.

## 3. How do you solve kinetic and potential energy problems?

To solve kinetic and potential energy problems, you need to identify the relevant variables such as mass, velocity, height, and any known energy values. Then, you can use the equations for kinetic and potential energy to calculate the energy values and solve for the unknown variable.

## 4. Can kinetic energy and potential energy be converted into each other?

Yes, according to the law of conservation of energy, energy cannot be created or destroyed but can be converted from one form to another. For example, when a ball is thrown into the air, its kinetic energy is converted into potential energy at the highest point of its trajectory, and then back to kinetic energy as it falls back down.

## 5. How does friction affect kinetic and potential energy problems?

Friction is a force that opposes motion, and it can affect both kinetic and potential energy problems. Friction can reduce an object's kinetic energy by converting it into thermal energy, and it can also decrease an object's potential energy by reducing its height or changing its shape.

Replies
3
Views
1K
Replies
55
Views
3K
Replies
2
Views
326
Replies
6
Views
1K
Replies
7
Views
4K
Replies
2
Views
1K
Replies
17
Views
3K
Replies
7
Views
1K
Replies
12
Views
974
Replies
13
Views
2K