Physics-Mechanical Energy

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Questions and Answers

What is the gravitational potential energy of a 0.5 kg book when it is 2 meters above a reference point?

  • 15 J
  • 20 J
  • 10 J (correct)
  • 5 J

How is mechanical energy defined in the context of physics?

  • The energy of an object due to motion only
  • The sum of kinetic energy and gravitational potential energy (correct)
  • The energy required to lift an object to a height
  • The total energy stored in an object

What does the equation ΔM.E = Wf−> M.Ef−M.E₁ = -f × d indicate?

  • The change in mechanical energy is dependent on displacement and friction force. (correct)
  • The initial mechanical energy is always greater than the final mechanical energy.
  • The relationship between work done and energy conservation.
  • The final mechanical energy can only be negative.

What would be the mechanical energy of a 0.1 kg bird flying at a speed of 10 m/s at a height of 50 m?

<p>55 J (A)</p> Signup and view all the answers

If the height of the book is increased from 2 meters to 3 meters, what will be its new gravitational potential energy?

<p>15 J (C)</p> Signup and view all the answers

Under what condition is mechanical energy conserved?

<p>When friction or air resistance is neglected. (C)</p> Signup and view all the answers

What does the notation M.E₁ = M.Ef signify?

<p>Initial mechanical energy is equal to final mechanical energy. (C)</p> Signup and view all the answers

Calculate the gravitational potential energy of the 0.5 kg book when it is 3 meters above the ground.

<p>15 J (C)</p> Signup and view all the answers

How is energy lost due to friction expressed in terms of heat?

<p>As q = |ΔM.E|, where ΔM.E is the change in mechanical energy. (D)</p> Signup and view all the answers

What condition determines that mechanical energy is not conserved?

<p>Existence of friction or air resistance. (B)</p> Signup and view all the answers

What is the work done by the normal force when the displacement is perpendicular?

<p>0 J (A)</p> Signup and view all the answers

How is the work done by friction calculated?

<p>$W_f = -f \times d$ (C)</p> Signup and view all the answers

If an object of mass 4 kg moves with a speed of 3 m/s, what is its kinetic energy?

<p>12 J (A)</p> Signup and view all the answers

What is the work done by a force of 10 N over a distance of 10 m?

<p>100 J (B)</p> Signup and view all the answers

How much work does a friction force doing 5 N over a distance of 10 m perform?

<p>-50 J (B)</p> Signup and view all the answers

What is the kinetic energy of a 103 kg car moving at 20 m/s?

<p>2 x 10^5 J (A)</p> Signup and view all the answers

How fast is a runner who covers 200 m in 40 seconds moving?

<p>5 m/s (B)</p> Signup and view all the answers

What is the formula for gravitational potential energy?

<p>G.P.E = m × g × h (C)</p> Signup and view all the answers

If an object has a mass of 50 kg at a height of 10 m, what is its gravitational potential energy?

<p>5000 J (C)</p> Signup and view all the answers

Which unit is used to measure gravitational potential energy?

<p>Joule (J) (D)</p> Signup and view all the answers

What is the formula for calculating the work done by a force along a displacement?

<p>$W = F imes d$ (D)</p> Signup and view all the answers

If a force of 50N is applied to move an object 4m in the direction of the force, how much work is done?

<p>100J (D)</p> Signup and view all the answers

What is the necessary condition for calculating work done by a force?

<p>The force must be constant and parallel to the displacement. (A)</p> Signup and view all the answers

What is the weight of an object if 600J of work is done in lifting it vertically by 3m?

<p>200N (B)</p> Signup and view all the answers

In the context of work done, which scenario will result in zero work?

<p>Lifting an object vertically with no displacement. (D)</p> Signup and view all the answers

Flashcards

Mechanical Energy

The total amount of energy possessed by an object due to its position and motion.

Conservation of Mechanical Energy

In a closed system, the total mechanical energy remains constant.

Non-conservative Forces

Forces that oppose motion, such as friction and air resistance.

Work Done

The energy transferred when a force causes an object to move.

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Heat Loss

The energy lost due to non-conservative forces is converted into heat.

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Kinetic Energy

The amount of energy an object possesses due to its motion.

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Work Done By Perpendicular Force

Work done by a force that acts perpendicular to the displacement is zero.

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Work Done By Friction

The work done by frictional force opposes the motion and is calculated by multiplying the frictional force by the distance.

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Joule (J)

The SI unit of energy. It represents the amount of work required to move an object with a force of 1 Newton over a distance of 1 meter.

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Work

The product of the force acting on an object and the displacement of the object in the direction of the force.

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Gravitational Potential Energy (G.P.E)

The energy an object possesses due to its position relative to a reference point.

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Mechanical Energy (M.E)

The total energy an object possesses, combining its kinetic energy (energy of motion) and potential energy (energy of position).

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Mechanical Energy Formula

The equation used to calculate the mechanical energy of an object. It combines the kinetic energy (1/2 * mv²) and gravitational potential energy (mgh).

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Kinetic Energy (K.E)

The energy an object possesses due to its motion.

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Reference Point

The reference point used to calculate the potential energy of an object. It dictates the height (h) used in the G.P.E calculation.

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Gravitational Potential Energy

The energy possessed by an object due to its position in a gravitational field. It is determined by mass, gravitational acceleration, and height.

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Kinetic Energy and Velocity

Kinetic energy is directly proportional to the square of the object's velocity. Doubling the velocity quadruples the kinetic energy.

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Work-Energy Theorem

The work-energy theorem states that the net work done on an object equals the change in its kinetic energy. This means that work is a measure of the energy transfer.

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Energy Units

The unit of energy in the International System of Units (SI) is the joule (J). 1 joule is equal to 1 kilogram times 1 meter squared divided by 1 second squared.

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Work done by a force

The force multiplied by the displacement of the object in the direction of the force.

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Study Notes

Mechanical Energy

  • Mechanical energy is either conserved or not conserved
  • If friction or air resistance is neglected, the principle of conservation of mechanical energy applies (mechanical energy is constant, M.Eᵢ = M.Ef)
  • If friction or air resistance exists, mechanical energy is not conserved (M.Eᵢ ≠ M.Ef). The change in mechanical energy (ΔM.E) equals the work done by friction (Wf), and the energy lost appears as heat (q = |ΔM.E|).

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