3/11 Flashcards
What is the formula to calculate Kinetic Energy (KE)?
KE = 1/2 m v²
What is the formula to calculate Potential Energy (PE)?
PE = mass × gravitational acceleration (9.8 m/s²) × height OR PE = Weight × Height
What units are used to measure Energy, Weight, Mass, Velocity, and Gravitational acceleration?
Energy = Joules
Weight = Newton
Mass = Kilograms
Velocity = m/s
Gravitational acceleration = 9.8 m/s²
A golf ball is struck with a mass of 2 kg. The ball leaves the club with a speed of 30 m/s. What is the ball’s energy?
KE = 1/2 × 2 kg × (30 m/s)² = 900 Joules
A ball is sitting at the top of a hill that is 21 m high. The ball weighs 15 N. What is the ball’s potential energy?
PE = Weight × Height = 15 N × 21 m = 315 Joules
A car is traveling with a velocity of 60 m/s and has a mass of 1200 kg. What is the car’s kinetic energy?
KE = 1/2 × 1200 kg × (60 m/s)² = 2,160,000 Joules
A golfer hits a golf ball with a mass of 1.3 kg. The ball leaves the club with a speed of 70 m/s. What is the ball’s kinetic energy?
KE = 1/2 × 1.3 kg × (70 m/s)² = 3185 Joules
A book is sitting on a bookshelf that is 20 m high. It weighs 8.5 N. What is the book’s potential energy?
PE = Weight × Height = 8.5 N × 20 m = 170 Joules
What is an example of Gravitational Potential Energy?
A rock sitting at the top of a hill has Gravitational Potential Energy.
What is an example of Elastic Potential Energy?
A stretched spring or rubber band has Elastic Potential Energy.
What is an example of Chemical Potential Energy?
A battery storing energy or food has Chemical Potential Energy.
What is an example of Magnetic Potential Energy?
A magnet held close to a metal object has Magnetic Potential Energy.
What is an example of Kinetic Energy?
A moving car or a person running has Kinetic Energy.
Where is there the most gravitational potential energy on a roller coaster? Why?
At the highest point of the track, because it has the greatest height relative to the ground.
Where is there the most kinetic energy on a roller coaster? Why?
At the lowest point of the track, because the car is moving at the greatest speed due to the conversion of potential energy into kinetic energy.
Would a roller coaster be able to make it to point 5 only by converting the gravitational potential energy from starting point 1? Explain.
No, because some energy is lost due to friction and air resistance, so the roller coaster would need an additional energy source to make it to point 5.
What is the law of conservation of energy? How does it relate to a roller coaster?
The law of conservation of energy states that energy cannot be created or destroyed, only converted from one form to another. In a roller coaster, gravitational potential energy is converted to kinetic energy, and vice versa, but the total energy remains constant (except for losses due to friction and air resistance).
What is the formula for calculating the potential energy of an object at a height?
PE = mass × gravitational acceleration (9.8 m/s²) × height
If a ball weighs 20 N and is lifted to a height of 10 meters, what is the potential energy of the ball?
PE = Weight × Height = 20 N × 10 m = 200 Joules
A 5 kg object is moving with a speed of 10 m/s. What is its kinetic energy?
KE = 1/2 × 5 kg × (10 m/s)² = 250 Joules
A car weighs 8000 N and is parked on a hill that is 15 meters high. What is the potential energy of the car?
PE = Weight × Height = 8000 N × 15 m = 120,000 Joules
A 10 kg ball is dropped from a height of 50 meters. What is its gravitational potential energy just before it is released?
PE = mass × gravitational acceleration × height = 10 kg × 9.8 m/s² × 50 m = 4900 Joules
What type of energy is associated with an object in motion?
Kinetic Energy
A person stretches a spring by 0.5 meters. What type of energy does the spring store?
Elastic Potential Energy
A chemical reaction occurs in a fuel cell that releases energy. What type of energy is released?
Chemical Potential Energy
A car at the top of a hill has 6000 Joules of gravitational potential energy. As the car goes down the hill, the energy is converted into which type of energy?
Kinetic Energy
What happens to the total energy of a system in a roller coaster ride as it goes up and down the track?
The total energy remains constant (conservation of energy), but it is constantly changing between potential and kinetic energy.
Why is there less kinetic energy at the top of the hill on a roller coaster?
Because the car is moving slower due to having more potential energy at the higher point and less kinetic energy.
What happens to a roller coaster car’s speed as it goes down a hill?
Its speed increases because gravitational potential energy is converted into kinetic energy.
What is the relationship between height and potential energy?
The higher an object is, the greater its potential energy, since potential energy increases with height.
If a 50 kg person is at the top of a 40 m high diving board, what is their potential energy?
PE = mass × gravitational acceleration × height = 50 kg × 9.8 m/s² × 40 m = 19,600 Joules
When a rubber band is stretched, what kind of energy does it have?
Elastic Potential Energy
How does a roller coaster demonstrate the conservation of energy?
The roller coaster converts gravitational potential energy into kinetic energy and vice versa, but the total energy (neglecting friction and air resistance) remains constant.
What energy transformation occurs as a roller coaster car moves from the top of the hill to the bottom?
Gravitational potential energy is converted into kinetic energy.
How does friction affect the energy of a roller coaster?
Friction causes the roller coaster to lose some energy, usually in the form of heat, which decreases its kinetic energy.
What is the formula for calculating gravitational potential energy?
PE = mass × gravitational acceleration (9.8 m/s²) × height
What type of energy is stored in a battery before it is used?
Chemical Potential Energy
A moving car has 450,000 Joules of kinetic energy. If its mass is 1500 kg, what is its speed?
KE = 1/2 × m × v² → 450,000 J = 1/2 × 1500 kg × v² → v = √(2 × 450,000 / 1500) = 24.49 m/s
What type of energy is stored in the fuel of a car before it is burned in the engine?
Chemical Potential Energy
How does the speed of an object affect its kinetic energy?
Kinetic energy increases with the square of the object’s speed (KE = 1/2 m v²), so doubling the speed results in four times the kinetic energy.
