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Questions and Answers
What is the unit of work in the MKS system?
What is the unit of work in the MKS system?
One Joule is equal to $10^7$ Ergs.
One Joule is equal to $10^7$ Ergs.
True
What is the equation for calculating kinetic energy?
What is the equation for calculating kinetic energy?
KE = 1/2 mv^2
Power is defined as the rate of doing ______.
Power is defined as the rate of doing ______.
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Match the following forms of energy with their descriptions:
Match the following forms of energy with their descriptions:
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What type of energy is possessed by an object raised to a certain height?
What type of energy is possessed by an object raised to a certain height?
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Renewable energy sources include fossil fuels.
Renewable energy sources include fossil fuels.
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What principle states that the total work done is equal to the total change in kinetic and potential energies?
What principle states that the total work done is equal to the total change in kinetic and potential energies?
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Study Notes
Work
- Work is the product of force and distance, acting in a direction parallel to the motion.
- Units:
- MKS: Joule (J) or Newton-meter (N⋅m) – representing the work done by a 1 Newton force over a 1-meter distance
- CGS: Erg or dyne-centimeter
- FPS: pound-foot (lb⋅ft) – indicating the work done by a 1 pound force over a 1-foot distance
Work Calculation for Various Scenarios
- Horizontal Force: Work (W) = Force (F) × Distance (d) If the force acts in the same direction as motion, W = +Fd. If the force opposes motion, W = -Fd.
- Force at an Angle: W= Fd cos(θ), where θ is the angle between the force and the direction of motion. This determines the component of the force that does work
- Vertical Force: W= Weight(w) × height (h) or W=mg*h where 'm' is mass, 'g' is acceleration due to gravity, and 'h' is height.
Work Done by Varying Forces
- W= 1/2 Fe, where 'e' is the elongation of a spring. Hooke's law states that strain is proportional to stress within the elastic limit of a material, meaning F1e2=F2e1.
Power
- Power is the rate of doing work, measured as work (or energy) divided by time. -Units: - Watt (W) = J/s (joules per second) - Horsepower (hp) - common unit for power -1hp ≈ 746 watts -1 hp = 550 lbft/s -1 hp ≈ 33,000 lb ft/min
Energy
- Energy is the ability to do work
- Forms of Energy:
- Kinetic Energy (KE) - energy due to motion; KE = 1/2mv² where 'm' is mass and 'v' is velocity
- Potential Energy (PE)
- Gravitational Potential Energy (GPE): Potential energy of an object due to its height; GPE = mgh
- Elastic Potential Energy (EPE): Potential energy in elastic objects or springs; EPE = 1/2 kx² where 'k' is the spring constant and 'x' is the displacement from equilibrium.
- Chemical Potential Energy: Energy due to chemical composition
- Forms of energy: Mechanical, chemical, thermal, light, sound, electrical, nuclear.
Energy Sources
- Renewable sources: Biomass, Geothermal, Solar, Water (tides), Wind
- Non-renewable sources: Fossil fuels (coal, oil, natural gas), Nuclear (uranium)
- Conventional sources: Thermal, geothermal, hydropower
- Non-conventional sources: Nuclear, tides, biomass, wind, solar,
Work-Energy Principle
- The total work done on an object equals the change in its kinetic energy plus the change in its potential energy (Wnet = ΔKE + ΔPE).
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Description
Test your knowledge on the concept of work in physics. This quiz covers various calculations involving horizontal forces, forces at angles, and vertical forces. Assess your understanding of units, formulas, and real-life applications of work.
