# 2.08 &2.09 Kinetic and Potential Energy

SCI06A~Johnson
2.08 & 2.09
Kinetic and Potential Energy
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Slide 1: Slide

This lesson contains 40 slides, with interactive quizzes, text slides and 3 videos.

Lesson duration is: 30 min

## Items in this lesson

SCI06A~Johnson
2.08 & 2.09
Kinetic and Potential Energy

#### Slide 2 -Video

Objective
We will identify and explain the difference between kinetic and potential energy.

#### Slide 3 -Slide

Agenda
• What is energy?
• What are the two types of energy?
• What makes them different?

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energy

#### Slide 6 -Video

You have 2 minutes to update a vocabulary card for energy.
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#### Slide 7 -Slide

kinetic energy
the energy of an object or substance because of its motion
potential energy
energy stored in an object based on its position.

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#### Slide 9 -Slide

What two variables influence kinetic energy?

#### Slide 10 -Open question

Kinetic Energy Formula

kinetic energy

#### Slide 12 -Mind map

Here are the steps to solve for kinetic energy
1. Plug your information into the formula
2. Square the quantity for speed.
3. Find one half of the mass.
4. Multiply these two numbers together.
5. Write the resulting answer in joules (J).

#### Slide 13 -Slide

Calculating Kinetic Energy

A marble has a mass of 0.05 kg. You shoot it out of your hand and send it moving at a speed of 2 m/s. How much kinetic energy does the marble have?
1. Plug your information into the formula.
2. Square the quantity for speed.
3. Find one half of the mass.
4. Multiply these two numbers together.
5. Write the resulting answer in joules (J).
ke=21mv2
ke=210.05kg(2sm)2

#### Slide 14 -Slide

Calculating Kinetic Energy

A marble has a mass of 0.05 kg. You shoot it out of your hand and send it moving at a speed of 2 m/s. How much kinetic energy does the marble have?
1. Plug your information into the formula.
2. Square the quantity for speed.
3. Find one half of the mass.
4. Multiply these two numbers together.
5. Write the resulting answer in joules (J).
ke=21mv2
ke=210.05kg(2sm)2
ke=210.05kg4s2m2

#### Slide 15 -Slide

Calculating Kinetic Energy

A marble has a mass of 0.05 kg. You shoot it out of your hand and send it moving at a speed of 2 m/s. How much kinetic energy does the marble have?
1. Plug your information into the formula.
2. Square the quantity for speed.
3. Find one half of the mass.
4. Multiply these two numbers together.
5. Write the resulting answer in joules (J).
ke=21mv2
ke=210.05kg(2sm)2
ke=210.05kg4s2m2
ke=0.025kg4s2m2

#### Slide 16 -Slide

Calculating Kinetic Energy

A marble has a mass of 0.05 kg. You shoot it out of your hand and send it moving at a speed of 2 m/s. How much kinetic energy does the marble have?
1. Plug your information into the formula.
2. Square the quantity for speed.
3. Find one half of the mass.
4. Multiply these two numbers together.
5. Write the resulting answer in joules (J).
ke=21mv2
ke=210.05kg(2sm)2
ke=210.05kg4s2m2
ke=0.025kg4s2m2
ke=0.1J

#### Slide 17 -Slide

A 50-kg girl is playing soccer. She runs toward the ball at a speed of 7 m/s. How much kinetic energy does she have as she runs? Calculate the answer to this problem using the equation KE = ½mv2.

#### Slide 18 -Open question

A 50-kg girl is playing soccer. She runs toward the ball at a speed of 7 m/s. How much kinetic energy does she have as she runs? Calculate the answer to this problem using the equation KE = ½mv2.
[4] KE = ½ (50 kg) (7 m/s)2
KE = (25 kg) (49 m/s)
KE = 1,225 J

The girl has 1,225 J of kinetic energy as she runs toward the soccer ball.

#### Slide 19 -Slide

Why Is Kinetic Energy Important?
Work changes the energy of an object. So if an object, such as a truck, has a lot of kinetic energy, it takes a lot of work to stop it. Imagine that there are two trucks that are the same mass (2,000 kg) and have the same braking force. Truck A is traveling 20 m/s, and Truck B is traveling 40 m/s. How do you think their kinetic energies will compare?

#### Slide 20 -Slide

Work changes the energy of an object. So if an object, such as a truck, has a lot of kinetic energy, it takes a lot of work to stop it. Imagine that there are two trucks that are the same mass (2,000 kg) and have the same braking force. Truck A is traveling 20 m/s, and Truck B is traveling 40 m/s. How do you think their kinetic energies will compare?

Potential Energy

#### Slide 23 -Video

Gravitational Potential Energy Equation

#### Slide 24 -Slide

A 2 kg bowling ball sits on top of a building that is 40 m tall. What is the KE?

#### Slide 25 -Open question

elastic potential energy
energy stored due to a change in shape in a material that tends to return to its original shape
elastic potential energy
energy stored due to a change in shape in a material that tends to return to its original shape
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#### Slide 26 -Slide

Example
Opening the trap winds the coil of the mousetrap’s spring tighter. The spring has to be held in place in this unnatural shape by a small metal bar. At this point, the spring has elastic potential energy. When the trap snaps shut, the spring loses elastic potential energy as it returns to its normal shape.

#### Slide 27 -Slide

What is another object that stores
elastic potential energy?

#### Slide 28 -Mind map

Potential Energy Equation

#### Slide 29 -Slide

A 2 kg bowling ball sits on top of a building that is 40 m tall. What is the PE?

#### Slide 30 -Open question

gravitational potential energy
energy invested in a body by lifting it against the force of gravity
gravitational potential energy
energy invested in a body by lifting it against the force of gravity
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#### Slide 31 -Slide

Gravitational Potential Energy
This skateboarder entering the half-pipe also has gravitational potential energy. As soon as she shifts her body, gravity will act on her, and she will travel down toward the base of the half-pipe.

#### Slide 32 -Slide

What is another object that stores
gravitational potential energy?

#### Slide 33 -Mind map

Gravitational Potential Energy Equation
The formula for weight that you used in previous lessons is (w = mg), or weight = mass (kg) x acceleration due to gravity (m/s2). By substituting mg for w in the original formula

#### Slide 34 -Slide

A 2 kg bowling ball sits on top of a building that is 40 m tall. What is the GPE?

#### Slide 35 -Open question

A 2-kg bowling ball is 2.5 meters off the ground on a post when it falls. Just before it reaches the ground, it is traveling 7 m/s.

What is the ke?

#### Slide 36 -Open question

A 2-kg bowling ball is 2.5 meters off the ground on a post when it falls. Just before it reaches the ground, it is traveling 7 m/s.

What is the gpe?

#### Slide 37 -Open question

Explain the difference between kinetic energy and potential energy.

#### Slide 38 -Open question

How does elastic potential energy differ from gravitational potential energy?

#### Slide 39 -Open question

Determine the gravitational potential energy of a 7.5-N object ready to fall from a height of 5 m. Show your work.