Questions and Answers
In which one of the following situations is zero net work done?
Which one of the following has the largest kinetic energy?
Which one of the following statements concerning kinetic energy is true?
Which one of the following situations is an example of an object with a non-zero kinetic energy?
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In which one of the following systems is there a decrease in gravitational potential energy?
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Which one of the following choices is an example of a conservative force?
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Which one of the following choices is an example of a non-conservative force?
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Complete the following statement: A force that acts on an object is said to be conservative if _____
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Which one of the following is not a unit of energy?
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Which one of the following statements concerning a donkey pulling a crate up a rough inclined plane at constant speed is false?
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Complete the following statement: Work may be expressed using all of the following units except _____
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In which one of the following situations will there be an increase in kinetic energy?
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Use the work-energy theorem to find the force required to accelerate an electron (m = $9.11 × 10^{-31}$ kg) moving along the x axis from $4.00 × 10^6$ m/s to $1.60 × 10^7$ m/s in a distance of $0.0125$ m.
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Two balls of equal size are dropped from the same height from the roof of a building. One ball has twice the mass of the other. When the balls reach the ground, how do the kinetic energies of the two balls compare?
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A rock is thrown straight up from the surface of the Earth. Which one of the following statements describes the energy transformation of the rock as it rises? Neglect air resistance.
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Study Notes
Work and Energy Concepts
- Zero net work occurs when an object is moved at constant velocity against friction, as in the case of a box being pulled across a rough floor.
- Gravitational potential energy decreases when an object moves downward, exemplified by a girl jumping down from a bed.
Kinetic Energy Highlights
- The Earth moving in its orbit around the sun has the largest kinetic energy compared to various objects like a raindrop or a jet airplane.
- Kinetic energy is always positive; it cannot be negative as per its definition.
- A satellite in geosynchronous orbit possesses non-zero kinetic energy, contrasting with stationary objects.
Forces and Work
- Conservative forces, such as elastic spring force, have work independent of the path taken, whereas non-conservative forces, like kinetic frictional force, do not.
- Work is measured in several units. However, watt is a power unit, not a unit of energy.
- Work done by gravity is significant; during constant speed movement up an inclined plane, the net work done is zero and gravitational potential energy increases.
Energy Units
- Energy units include joules, newton-meters, and foot-pounds, but watt is not a unit of energy.
- To find force using the work-energy theorem, calculations involve mass, initial and final velocities, and distance traveled, such as determined for an electron moving in an electric field.
Energy Transformations
- When a rock is thrown upward, kinetic energy decreases while potential energy increases, illustrating the conversion of energy types as the object rises.
- In free fall, two objects of differing masses dropped from the same height will have kinetic energies proportional to their masses at ground impact; the heavier one possesses greater kinetic energy.
Practical Examples and Applications
- Accurate calculations of forces for accelerating objects require understanding of mass and energy dynamics, illustrated through specific numerical examples.
- Situations involving energy storage and transfer illustrate principles of physics in everyday contexts, reinforcing theoretical concepts through tangible examples.
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Description
Test your understanding of key physics concepts with this set of flashcards. Each card presents a question or scenario related to work and energy in physics. It's perfect for quick revision or exam preparation.
