Forces and Energy
- Created by: Former Member
- Created on: 21-05-19 16:10
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- Section 20 - Forces and Energy
- Energy transfers and systems
- Energy is transferred between stores mechanically, electrically, by heating or by radiation
- Kinectic, thermal, chemical, gravitational potential, elastic potential, electrostatic, nuclear, magnetic
- Energy is transferred between stores and objects in system
- Energy can be dissipated in wasteful ways too e.g. heat
- A closed system is defined so that the net energy change is 0
- If the system is a pan of water and camping stove, energy is transferred from the chemical store of the gas to the thermal store of the pan and water, increasing the temperature
- If the system is a box being lifted, energy is transferred to its kinetic and potential energy stores
- If the system is a toothbrush, energy is transferred from chemical store of the battery to the kinetic stores of the bristles. Energy is also dissipated by heat and sound.
- Energy is transferred between stores mechanically, electrically, by heating or by radiation
- Work Done and Power
- Power = rate of energy transfer
- The larger the power of an object, the more work it does per second
- If a force moves an object, work is done
- Energy is transferred mechanically from one store to another
- Forces
- Contact forces when the objects are touching each other
- Non-contact forces have interacting fields but aren't touching
- Two objects feel an equal but opposite force, called an interaction pair, that can be shown by arrows
- Free-body force diagrams show all the forces acting upon an object or system with arrows of size relative to their magnitudes
- A resultant force is the overall force on a point or object
- Forces and Vector Diagrams
- Scale Drawings
- Draw all the forces acting on an object "tip to tail"
- Then draw a straight line from the first force to the end of the last force - this is the resultant force
- Measure the length to find the magnitude and the angle to find the direction
- Then draw a straight line from the first force to the end of the last force - this is the resultant force
- Draw all the forces acting on an object "tip to tail"
- If all of the forces on an object combine to give a resultant force of 0, the object is in equilibrium
- You can split a force into components and measure each one to measure the overall force
- Scale Drawings
- Energy transfers and systems
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