Stile Energy Conservation Test

The 400 kg roller coaster carriage reaches a velocity of 20 m/s (72 km/h) just before entering a corkscrew. How much kinetic energy does it have at this point? Hint: Kinetic Energy= Mass x Velocity2

160,000 J

A roller coaster carriage with a mass of 400 kg is raised to an initial height of 50 m. How much potential energy does it have at this point? Potential Energy= Mass x Gravity(9.8) x Height

196,000 J

An experimental wave power system is found to have an efficiency of 80%. This means that for every 100 J of energy in the waves, ____ J is converted into electricity.

80

Explain how the energy of a roller coaster changes as it descends from one high point and climbs to the next one. You can ignore friction and air resistance. Use energy terms: Kinetic, Potential, height, and velocity.

Answer may vary but must be similar to: "As it descends, its initial gravitational potential energy is converted into kinetic energy, reflected in the fact that it speeds up. At the lowest point, its gravitational potential energy reaches a minimum and its kinetic energy reaches a maximum. As it climbs, its kinetic energy is converted back into gravitational potential energy, which is proportional to the height."

Explain the energy transformations that allow hydroelectric dams to extract useful energy from nature. Hint: Look back at the picture of the hydroelectric dam and and explain the energy transformations between 1 & 2 and then between 2 & 3. Use Terms as: Kinetic energy, potential energy, and Thermal (friction) energy

Answer may vary but must be similar to: Hydroelectric dams harness useful energy from the gravitational potential energy of water as it tries to make its way from mountains to the sea. 1. The water stored behind a dam wall has gravitational potential energy because it is located at a certain height above sea level. 2. When a gate is opened, the water flows through a channel so its gravitational potential energy is converted into kinetic energy. 3. The flowing water spins a turbine which then spins a generator. 4. The generator converts the kinetic energy of the spinning motion into electrical energy, using magnets and copper wire. 5. The electrical energy (electricity) produced is in a form that can be easily transported and then used in homes and businesses.

Does the water coming out from the turbines move at the same speed as the water going into them? Why?

Answer may vary but must be similar to: No because the energy transformation takes place when the water hits the propellor. The kinetic energy pushes the propellors and is converted into electrical energy and the remaining bit of kinetic energy is used to move the water out of the bottom of the turbine.

If a man skateboarded down a slope, would he continue rolling forever? If not, what would stop him and what kind of energy transformation is this?

Answer may vary but must be similar to: No he would not continue rolling forever. Friction and air resistance would stop him. This type of energy transformation is kinetic energy to heat and sound energy.

In your own words, state the law of conservation of energy.

Answer may vary but must be similar to: The law of conservation of energy states that energy can never be created nor destroyed, only transferred between objects or transformed from one type to another.

List three examples in which an object's energy is transformed back and forth between potential and kinetic energy.

Answer may vary but must include everyday objects that change energy types like: Roller coaster Yo-Yo Ball

In the diagram above, the energy transformation(s) between 1 and 3 that are used to generate electricity are:

Gravitational Potential to Kinetic to Electrical

What 3 things are needed for the potential energy formula?

Gravity, Height, and Mass

The amount of energy carried by water waves depends on their ____________ and ____________.

Height and Period

Assuming there is no friction or air resistance, what energy transformation occurs as a roller coaster climbs a hill?

Kinetic to Gravitational Potential

What 2 thins are needed for the kinetic energy formula?

Mass and Velocity

The pink circles represent energy losses that reduce the efficiency of the system. Which 3 of these does this include:

Sound energy, Heat Energy, and Kinetic energy

Friction and air resistance transform some of a carriage's kinetic energy into:

Thermal energy and Sound energy

Hydro (water) power is the extraction of useful energy from what 3 things?

Tides, Rivers/Lakes, and Waves

True or False, At any point in time, the potential plus the kinetic always equals the total amount of energy.

True

Most roller coasters aren't given any help by motors after being raised up to the top of the first hill. This height determines the maximum gravitational and kinetic energy of the roller coaster on its journey because:

energy is never created nor destroyed, just transformed or transferred

Adding passengers to a roller coaster carriage ____________ its kinetic energy.

increases

Adding passengers to a roller coaster carriage ____________ its potential energy.

increases

What type of energy depends on velocity/speed?

kinetic

What type of energy depends on height?

potential