Topic 1: Energy (Paper 1) Flashcards
~ Kinetic Energy ~
* What is kinetic energy?
* what is the equation for kinetic energy?
- Kinetic energy is the energy stored in moving objects
- Ek (J) = 0.5 x mass (kg) x velocity (m/s)²
~ Elastic Potential Energy ~
* What is elactic potential energy?
* What is the relationship between the extension and force applied?
* What happens if we apply too great a force?
* What is the equation for elastic potential energy?
- Elastic potential energy is the store of energy after doing work in a stretched spring.
- The force applied (N) is directly proportional to the extention (m).
- If too great a force is applied, the spring is stretched beyond the limit of proportionality and won’t return back to the original length if the force is removed.
- Ee (J) = 0.5 x spring constant (N/m) x extentsion (m)²
~ Gravitational Potential Energy ~
* What is gravitational potential energy?
* What is the equation for gravitational potential energy?
- Gravitational potential energy is the energy stored in an object due to its position above the Earth’s surface.
- Ep (J) = mass (Kg) x gravitational fireld strength (N/kg) x height (m)
**~ Specific Heat Capacity ~ **
* What is specific heat capacity?
* What is the equation for specific heat capacity?
- The amount of energy required to increase the temperature of 1kg of a substance by 1°C
- Change in thermal energy (J) = mass (kg) x specific heat capacity (J/kg°C) x change in temperature (°C)
**~ Conservation of energy ~ **
* What is the law of conservation of energy?
- Energy can’t be created or destroyed.
~ Systems ~
* What is a system?
* What happens in a closed system?
- An objest or a group of objects/
- In a closed system, no energy can enter or leave
How can we reduce unwanted energy transfers by reducing friction in the case of a pendulum?
By using a lubricant, or by removing the air particles around the pendulum
Why does a bungee jumper not return to the original height?
Energy is dissipated as thermal energy due to friction with air particles and stretching effects because the rope is not fully leastic
~ Work Done ~
* What happens when work is done?
* What is mechanical work?
* What is electrical work?
* What is the equation for work done?
- Energy is transferred from one store to another.
- Using a force to move an object.
- When a current transfers energy.
- Work done (J) = force (N) x Distance (m)
~ Power ~
* What is power?
* What are the two equations for power?
- Power is the rate at which energy is transferred or the rate at which work is done.
- Power (W) = energy transferred (J) ÷ time (s)
- Power (W) = work done (‘J) ÷ time (s)
**~ Efficiency ~ **
* What is the equation for efficiency?
* How can we increase the efficiency of a pan on a hob?
- Efficiency (%) = (useful energy output (J) ÷ total energy input (J)) x 100
- wider base; lid; heating element inside water; plastic walls and lid (kettle) instead of metal - insulator
**~ Insulation ~ **
* What affects the cooling of a building?
* Why is the cavity between the external brick and the internal breezeblock paaced with insulating material?
* How can we reduce the loss of thermal energy of a house?
- Thermal conductivity of the materials
- This insulating material has a very low thermal conductivity so less thermal energy is lost through the walls.
- double glazed windows (lower thermal conductivity); loft insulation; build house with thicker walls; wall insulation
**~ Required Practical~ **
* Describe a method to determin the specific heat capacity of a material.
* What are the sources of inaccuarcy in this experiment?
- Record the mass of the material with a balance.
- Place a thermometer and an immersion heart into the substance.
- Record this starting temperature.
- Wrap the substance with an insulating material to reduce loss of heat to surroundings
- Connect a houlemeter and powerpack to the immersion heater.
- Turn on and leave for 30min.
- Read the number of joules of energy passed into the immersion heater and the final temperature of the substance.
- Then work out the SHC using the formula.
- heat passing out of the substance (use insulating material), not all thermal energy passed into the substance (ensure heater is fully submerged), incorrect thermometer reading (use an electronic temperature probe)
**~ Required Practical~ **
* How can we invesigate the effect of different thicknesses of the same insulating material?
1.Fill a beaker with 80cm³ of hot water.
2.Measure the temperature of the water every 3min for 15mins
3.Repeat experiment but wuth added layers of insulating material each time.
~ Required Practical ~
* Describe a method to investigate the effect of different thermal insulators.
- Place a smaller beaker inside a larger beaker.
- Use a kettle to boil some water and transfer 80cm³ of the hot water into the small beaker.
- Use a piece of cardboard as a lid for the large beaker (with a hole for a thermometer)
- Place thermometer into the hole.
- Record starting temperature.
- Repeat experiment with the same volume of hot water but with an insulating material (E.g. bubble wrap), to fill the gap between the two beakers.
- Repeat again with a different insulating material, e.g. wool
