PHYS132 Physics for Engineers: Work, Energy, and Power
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A comprehensive set of flashcards to review key concepts in Work, Energy, and Power.
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What theorem is applied to obtain quantitative and qualitative conclusions of a given system?
The work-energy theorem.
What two quantities are used to analyze the motion of objects in this physics course?
Energy and momentum.
What is the SI unit of work?
Joule (J).
How is work calculated when a force is applied to an object during linear displacement?
W = F × d × cos(θ), where θ is the angle between the force and the direction of displacement.
What is the formula for calculating total work done by multiple forces acting on an object?
Total work is the algebraic sum of the work done by individual forces.
What is the work done when the force exerted is perpendicular to the direction of displacement?
No work is done.
What effect does gravitational potential energy have in a system when the energy is transformed?
It transforms into kinetic energy.
What is the relationship between work and kinetic energy?
The net work done on an object is equal to the change in its kinetic energy.
Define kinetic energy.
The energy an object possesses due to its motion.
What formula expresses the kinetic energy of an object in motion?
KE = 1/2 mv², where m is mass and v is speed.
What is potential energy?
The energy possessed by an object due to its position or configuration.
How is gravitational potential energy calculated for an object at a height h?
PE = mgh, where m is mass, g is the acceleration due to gravity, and h is height.
What type of force is a conservative force?
A force for which the work done is independent of the path taken.
Give an example of a conservative force.
Gravitational force.
What is a nonconservative force?
A force for which the work done depends on the path taken.
Name an example of a nonconservative force.
Friction.
What is the principle of conservation of mechanical energy?
In the absence of nonconservative forces, the total mechanical energy remains constant.
What does power measure in physics?
The rate at which work is done.
What is the SI unit of power?
Watt (W).
How is one watt defined in terms of work?
One watt is the rate at which one joule of work is done in one second.
Explain what is meant by average power.
Average power is calculated as the work done divided by the time interval.
What relationship does power have with force and velocity?
Power can also be expressed as P = F Ă— v, where F is the applied force and v is the speed of the object.
Define the work-energy principle.
The net work done on an object is equal to the change in its kinetic energy.
What is the work done by a constant force?
It is the force multiplied by the displacement in the direction of the force.
What is the formula to calculate work done against gravity?
W = mgh, where h is the height lifted.
If the net work on the object is zero, what can be said about its kinetic energy?
The kinetic energy remains constant.
What error might occur if one does not consider angles when calculating work?
Incorrect work calculation since only the component of force parallel to the displacement does work.
What happens to the total mechanical energy in a system when nonconservative forces like friction are present?
The total mechanical energy decreases.
When lifting an object to a height h, what type of energy is being increased?
Gravitational potential energy.
Why is it important to measure both kinetic and potential energy in a physics problem?
To understand energy conservation and transformations in a system.
What does it mean for energy to be conserved in a closed system?
The total energy remains constant; it transforms but does not reduce or increase.
Describe how energy is transferred when an object does work.
Energy is transferred from the object applying a force to the object being moved.
In physics, what is meant by net work?
The total work done on an object, considering all forces acting on it.
What is the potential energy of an object if the height is zero?
Zero potential energy.
What occurs to kinetic energy when an object slows down?
The kinetic energy decreases.
In mechanical systems, what role does friction play?
Friction does work against motion and converts mechanical energy into thermal energy.
How does mass affect potential energy?
Potential energy increases linearly with mass at a constant height.
What must be considered when calculating work done on an incline?
The angle of the incline affects the component of gravitational force acting along the incline.
What is the work-energy theorem expressed mathematically?
Wnet = ΔKE = KEfinal - KE_initial.
What does a negative work indicate about the direction of force?
The force is acting opposite to the direction of displacement.
How do you calculate the work done by a spring?
W = 1/2 kx², where k is the spring constant and x is the displacement from equilibrium.
What is critical to remember about work done when the force is variable?
Integration is required to calculate work done with varying forces.
What must happen to energy during a transformation from potential to kinetic energy?
The total mechanical energy remains constant if only conservative forces are acting.
How is work done on the object calculated when a force varies with position?
By finding the area under the force vs position curve.
How does the angle of force applied affect the amount of work done on an object?
Work is maximized when the angle is zero, causing maximum force in the direction of displacement.
In example problems, when an object is lifted against gravity, why is potential energy important?
It helps us determine how much work was done to lift the object.
What indicates that work is done on an object?
An object is displaced in the direction of an applied force.
What would the work done by a constant force be if there is no movement?
The work done would be zero.
When calculating work done, why must the displacement be in the same direction as the force?
Because only the component of force in the direction of displacement contributes to work.
In determining speed at a point, what energy consideration must be made?
The total mechanical energy at that point must be equal to the initial energy minus work done.
How do puppeteers use the concepts of work and energy?
They apply force to strings causing energy transfer to move puppets, showing work in action.
What happens to mechanical energy when an object climbs a hill?
As potential energy increases, kinetic energy decreases if no external work is done.
How do varying forces complicate work calculations?
The work cannot simply be calculated with a single force value but must account for changes.
What kind of relationship exists between work, energy, and power?
Work done over time defines power, and energy is the capacity to perform work.
In a closed system with conservative forces, how is energy conserved?
Energy simply transforms between kinetic and potential forms but remains total fixed.
Define how energy changes when an object is in free fall.
Potential energy decreases while kinetic energy increases until impact.
What should you do first when solving energy-related problems?
Identify which types of energy are present and how they transform.
Why is work considered a transfer of energy?
Because performing work changes the energy state of an object.
What concept connects the force acting on an object, displacement, and the resulting energy?
Work, as it relates force applied over distance.