Unit 4 is about Energy. In this unit, we are going to explore how to use pie chart and bar chart to represent transferring of energy, how to use energy equations and concept of conservation of energy to solve problems and etc.
Unit 4 Notes
Key terms:
- Energy (E) - Measurement of the ability to do work. Energy allows us to make changes. SI unit: joule (J).
- Work (W) - A transfer of energy. It is the change in energy by the transfer of energy from one system to another. Scalar quantity with units of joules (J).
- Joules (J) - SI unit for energy. Applying a net force of 1N to an object over a displacement of 1m requires 1 J of energy. [ 1J = 1N*1m = 1 kg*m^2/s^2 ]
General equations:
GRAPH
The force applied to an object can be graphed as a function of the position of the object. Area under a F V.S. Δx graph is the energy transferred through working. Areas above the position axis are positive work and areas below the axis are negative work. If the force is not constant, we can divide the graph into sections with simpler shapes and add up the work in each section.
The force applied to an object can be graphed as a function of the position of the object. Area under a F V.S. Δx graph is the energy transferred through working. Areas above the position axis are positive work and areas below the axis are negative work. If the force is not constant, we can divide the graph into sections with simpler shapes and add up the work in each section.
- For example, to find the total work done on the object described in Figure 1, we can say:
TYPES OF ENERGY
Potential Energy - stored energy, energy caused by the object's position
Kinetic Energy - the energy of motion
Mechanical Energy = Potential Energy + Kinetic Energy
Kinetic Energy (KE)
Potential Energy - stored energy, energy caused by the object's position
Kinetic Energy - the energy of motion
Mechanical Energy = Potential Energy + Kinetic Energy
Kinetic Energy (KE)
- Energy stored in the motion of mass
- measured by the speed / velocity of an object
- change in velocity and mass can influence KE
- Energy stored in the distance between the object and its "source" in a gravitational field
- measured by the amount of distance between objects
- change in height and mass can influence GPE
- Energy stored in the elastic force field. Stored in the distortion of an object
- measured by the amount of compression or stretch of an object
- change in stretch and spring constant (k) can influence EPE
- Energy stored in the random motion on the molecular level of an object's composition
- measured by the temperature of an object
- change in the temperature of the object can influence Eint
- It is a law of physics that states that the force (F) needed to extend or compress a spring by some distance x scales linearly with respect to that distance.
Law of Conservation Energy
- Energy is ALWAYS Conserved
- The total energy of an isolated system is constant. Energy is neither created nor destroyed, it can only be transformed from one form to another or transformed from one form to another or transferred from one system to another.
Ways of Energy Transformation
Energy Conservation Equations
E initial+W+Q+R=E final
- Energy can be transferred through working (W), heating (Q), or radiating (R).
- Energy can be transferred by exerting an EXTERNAL push or pull on a system
- Temperature is the average amount of kinetic Energy in an object
- A temperature difference between system and surroundings causes energy to transfer from a warmer object to a cooler one
- matter loses energy by radiating light, and it gains energy when it absorbs light
Energy Conservation Equations
E initial+W+Q+R=E final
LOL DIAGRAMS
POWER
Power (P) - RATE at which work is done (or energy is transferred). SI units of Watt (W)
Watt (W) - Power equivalent to transferring 1 joule of energy per second. SI units of (kg*m^2/s^3)
Power (P) - RATE at which work is done (or energy is transferred). SI units of Watt (W)
Watt (W) - Power equivalent to transferring 1 joule of energy per second. SI units of (kg*m^2/s^3)
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