conservation of energy and power

• A 25 kg mass or a 30 kg mass going 5 m/s. Which one has more kinetic energy?

  30 kg mass
• 10 kg masses, one going 75 m/s, one going 45 m/s.


  the one going 75 m/s
• A car at rest or a car rolling down a hillWhich one has more kinetic energy?

  rolling down
• Which one has more potential energy? A plane on the ground or a plane in the air?

  the plane in the air
• Which one has more potential energy?A car at the top of the hill or the bottom of a hill?


  At the top
• Which one has more potential energyA 25 kg mass or a 30 kg mass at the top of a hill?

  30 kg
• A rolling ball has 18 joules of kinetic energy and is rolling 3 m/s. find its mass?

  4 kg
• A 8 kg cat is running 4 m/s. How much kinetic energy does it have?

  64 J
• A 4kg rock is rolling 10 m/s. Find its kinetic energy

  200 J
• A rock is at the top of a 20 meter tall hill. The rock has a mass of 10 kg. How much potential energy does it have?

  1960 J
• How high up is a 3 kg object that has 300 joules of energy?

  10.2 m
• What is the number you use for gravity?

  9.8
• True or False. Anything that causes change must have energy.

  True
• True or False. Kinetic energy is energy in the form of motion.

  True
• True or False. The joule is a unit used to measure energy.

  True
• True or False. Chemical energy stored in food cannot be transformed into mechanical energy?


  False. It can be transformed into movement (mechanical energy)
• True or False. Gravitational potential energy is released by burning substances?


  False. Chemical Potential Energy is released.
• What is the energy stored in foods and fuels?

  Chemical potential energy
• How do you demonstrate the conservation of energy on a daily basis? You can start off with getting chemical energy from breakfast.

  Chemical Potential Energy from breakfast is used by my body for mechanical energy during movement, and thermal energy to keep my body warm.
• True or False. Power is work done over a distance

  False. Power is work done over time.
• True or False. Energy is the ability to cause change

  True
• The unit of power is the _________________

  Watt (W)
• The kinetic energy of an object increases as its ____ increases.

  mass or velocity.5 x mass x velocity^2 = kinetic energy
• Increasing the speed of an object ____ its potential energy.


  does not affect.Gravitational PE = mass X 9.8 X heightspeed is not included into the equation so it does not affect.
• According to the law of conservation of energy, the total amount of energy in the universe ____.


  stays the sameremains constant
• A wagon is pulled at a speed of 0.50 meters/sec by a horse exerting an 2,100-newton horizontal force. What is the power of this horse?

  Power also equals Force times velocity.2100 x .5 = 1050
• Which required more power, walking or running up the steps yesterday? Explain in terms of the time it took to go up the steps.


  Power = Work divided by timerunning up the steps because it took less time to do the work.You are dividing work by a smaller number if it takes less time.
• True or False. Friction changes the energy of an object into mechanical energy.


  False.it changes energy into thermal energy.
• Into what kind of energy did you transform your chemical potential energy on Wednesday while you went up the stairs?

  gravitational potential energy
• Give me an example of elastic potential energy

  rubber bands, springs, etc
• A motor does 5,000 joules of work in 20 seconds

  5000 divided by 20 = 250 W
• Energy is measured in joules (J).