Potential and Kinetic Energy Background
Potential energy is stored energy. Often, the energy is stored due to an object's position, such as its position above the ground. The amount of potential energy depends on the height of the object above the ground. The amount of potential energy also depends on the mass of the object.
Kinetic energy is energy of motion. Objects in motion have kinetic energy. Kinetic energy depends on how fast the object is moving. Kinetic energy also depends on the mass of the object.
When an object is up high, it has potential energy. If it falls or rolls downward, its potential energy is converted to kinetic energy as it falls or rolls downward. As its kinetic energy increases, its speed increases.
Imagine a ball rolls down a hill. Its potential energy decreases, and its kinetic energy increases.
Now Imagine that ball hits a plastic cup at the bottom of the hill. The ball's kinetic energy can be used to move that cup. The more kinetic energy the ball has, the more it can move the cup it hits at the bottom of the hill.
The principle behind potential and kinetic energy is that energy can be transferred and transformed between different forms. Potential energy is the energy that is stored in an object due to its position or condition. In the case of an object's position above the ground, the higher the object is, the more potential energy it has. The formula to calculate potential energy is P.E. = mgh, where "m" is the mass of the object, "g" is the acceleration due to gravity, and "h" is the height of the object above the ground.
On the other hand, kinetic energy is the energy of motion. When an object is in motion, it possesses kinetic energy. The formula to calculate kinetic energy is K.E. = 1/2mv^2, where "m" is the mass of the object and "v" is the velocity or speed of the object.
When an object gains height or is lifted higher, its potential energy increases, and when it loses height, its potential energy decreases. The potential energy is converted into kinetic energy as the object falls or rolls downward, resulting in an increase in its speed. This conversion is governed by the law of conservation of energy, which states that energy cannot be created or destroyed, only transferred or transformed from one form to another.
In the example of the ball rolling down a hill, as it moves downhill, gravity acts on it to convert its potential energy into kinetic energy, causing the ball to gain speed. When the ball hits the plastic cup at the bottom of the hill, its kinetic energy can be used to move the cup. The amount of kinetic energy the ball possesses determines how much it can move the cup. The greater the kinetic energy, the more forceful the impact and the more movement the cup will experience.
1. How will changing each property affect the potential energy of an object? (2 points)
This will increase the object's potential energy.
increasing the object's height above the ground
decreasing an object's height above the ground
increasing the object's mass
decreasing the object's mass
This will decrease the object's potential energy.
Increasing the object's height above the ground will increase its potential energy. This is because potential energy is directly proportional to the height of the object above the ground. The higher the object is, the greater potential energy it will have.
Decreasing the object's height above the ground will decrease its potential energy. As the object gets closer to the ground, its potential energy decreases because there is less distance for it to fall and less potential for it to be converted into kinetic energy.
Increasing the object's mass will also increase its potential energy. Potential energy is directly proportional to the mass of the object. The greater the mass, the greater potential energy it will have.
Decreasing the object's mass will decrease its potential energy. As the mass decreases, so does the potential energy. The amount of potential energy is dependent on the mass of the object, so reducing the mass will result in less potential energy.
2. How will changing each property impact the kinetic energy of a moving object?
(2 points)
speed will increase kinetic energy.
mass will
increase kinetic energy.
speed will decrease kinetic energy.
mass will decrease kinetic energy.
:: Increasing
:: Decreasing
Increasing the speed of a moving object will increase its kinetic energy. Kinetic energy is directly proportional to the square of the velocity or speed of the object. Therefore, increasing the speed will result in a greater amount of kinetic energy.
Increasing the mass of a moving object will also increase its kinetic energy. Kinetic energy is directly proportional to the mass of the object. The greater the mass, the greater kinetic energy it will have.
Decreasing the speed of a moving object will decrease its kinetic energy. Kinetic energy is directly proportional to the square of the velocity. Therefore, reducing the speed will result in a lower amount of kinetic energy.
Decreasing the mass of a moving object will also decrease its kinetic energy. Kinetic energy is directly proportional to the mass of the object. As the mass decreases, so does the amount of kinetic energy.
Investigation 1- Using Balls with Different Masses
Experimental Questions
How does increasing mass affect the energy of a ball rolling down a hill?
Hypothesis
A ball rolls down a hill and hits a cup at the bottom. Then a ball with a larger mass rolls down the same hill and hits the cup at the bottom. If the mass of a rolling ball is larger, then its kinetic energy will be
Increased.
Safety
⚫ Wear closed-toe shoes.
⚫ Carefully follow all instructions.
⚫ Wear safety glasses whenever working in a lab,
Procedure 1
1. As shown in the video, allow ball of lower mass to roll down the ramp and move the cup placed at the bottom of the ramp.
2. Measure the distance the ball was able to push the cup. Record this distance in data chart 1.
3. Repeat the process with ball of higher mass.
Video - You must watch this to collect data.
Clarification from video-The video shows two different balls. The colorful ball has a lower mass. The stainless steel ball has a higher mass. When the video talks about "increasing the mass of the ball," it is referring to switching to the ball with greater mass. (We can't make an individual ball suddenly have a greater mass, so "increasing the mass of the ball really means switching to a ball with more mass. The ball's mass does not increase when it rolls down the ramp. An increase in kinetic energy comes from switching to a ball with more mass.)
Experimental Questions:
How does increasing mass affect the energy of a ball rolling down a hill?
Hypothesis:
If the mass of a rolling ball is larger, then its kinetic energy will be increased.
Procedure:
1. Set up a ramp with a cup placed at the bottom.
2. Start with a ball of lower mass and allow it to roll down the ramp.
3. Measure and record the distance the ball was able to push the cup.
4. Repeat the process with a ball of higher mass.
5. Measure and record the distance the ball was able to push the cup.
6. Compare the recorded distances for the two balls.
Safety Precautions:
1. Wear closed-toe shoes to protect your feet.
2. Follow all instructions carefully.
3. Wear safety glasses whenever working in a lab to protect your eyes.
Data Table 1
Drag the correct distance measurements into the table.
You must get this data from the video. Do not guess.
(2 points)
distance cup traveled
ball with lower mass
ball with larger mass
#25 cm
:: 80 cm
#100 cm
# 279.5 cm
300 cm
Data Table 1:
Distance Cup Traveled:
Ball with lower mass: 25 cm
Ball with larger mass: 279.5 cm
In this experiment, a ball rolls down a hill and hits a cup at the bottom. The hypothesis predicted if a ball with higher mass is used, that ball's kinetic energy at the bottom of the hill will be:
A. Increased
B. Decreased
C. Unchanged