Work, Energy and Power

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Questions and Answers

A box is pushed horizontally across a floor. Which scenario would result in zero work being done on the box?

  • The box is lifted vertically at a constant speed.
  • The box is moved at a constant velocity across a rough floor.
  • The box remains stationary despite the applied force. (correct)
  • The applied force is equal to the kinetic friction force, resulting in no change in velocity.

A crane lifts two identical steel beams to different heights. Beam A is lifted to 10 meters, and Beam B is lifted to 15 meters. Which of the following statements is true regarding the gravitational potential energy (GPE) of the beams?

  • The GPE of both beams is zero because steel is not affected by gravity.
  • Beam A has more GPE than Beam B.
  • Beam B has more GPE than Beam A. (correct)
  • Beam A and Beam B have the same GPE.

A car accelerates from rest to a certain speed. What happens to the kinetic energy of the car if its mass is doubled while reaching the same speed?

  • The kinetic energy is halved.
  • The kinetic energy is doubled. (correct)
  • The kinetic energy is quadrupled.
  • The kinetic energy remains the same.

A motor lifts a heavy load 5 meters in 10 seconds. If a more powerful motor lifts the same load the same distance in 5 seconds, how does the work done compare between the two motors?

<p>Both motors do the same amount of work. (C)</p> Signup and view all the answers

A roller coaster car is at the top of a hill, possessing maximum gravitational potential energy. As it descends, the GPE converts to kinetic energy. Assuming negligible friction, what happens to the total energy of the roller coaster car?

<p>The total energy remains constant. (A)</p> Signup and view all the answers

Flashcards

What is Work?

Force causing movement in the force's direction.

What is Energy?

The ability to do work.

What is Kinetic Energy (KE)?

Energy of motion.

What is Gravitational Potential Energy (GPE)?

Energy stored due to height.

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Law of Conservation of Energy?

Energy is only transferred. Total energy remains constant.

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Study Notes

Work

  • Work occurs when a force causes an object to move in the same direction as the force.
  • Work equals force times distance (W = F × d).
  • W is work measured in Joules (J).
  • F is force measured in Newtons (N).
  • d is distance measured in meters (m).
  • Work is zero if there is no movement or if the force is perpendicular to the motion.

Energy

  • It is the ability to do work.

Types of Energy

  • Kinetic Energy (KE) is the energy of motion, calculated as KE = (1/2)mv².
  • m is mass measured in kilograms (kg).
  • v is velocity measured in meters per second (m/s).
  • Gravitational Potential Energy (GPE) is energy stored due to height, calculated as GPE = mgh.
  • g is gravity (9.8 m/s²).
  • h is height measured in meters (m).
  • Other types of energy include elastic, chemical, thermal, and electrical.

Law of Conservation of Energy

  • Energy cannot be created or destroyed, only transferred.
  • The total energy remains constant in a system.

Power

  • Power is the rate of energy transfer or work done per second and is calculated as P = W/t.
  • P is power measured in Watts (W).
  • t is time measured in seconds (s).

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