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You use the equation for finding potential energy (PE=mgh) to find that a marble with a mass of20g held in the air has 0.2 J of potential energy. You then drop the marble. Work the follow outon a piece of paper carefully showing all work:(a) Since you know that the Conservation of Mechanical Energy applies(TE=KE+PE), use the fact there is no kinetic energy when the marble is heldstill in the air to find the total energy that the marble has when it's dropped.(b) Since you know that the total energy is conserved so that the total energy ofthe marble that you found in (a) equals the total energy of the marble rightbefore it hits the ground, write the equation for TE of the marble right beforeit hits the ground subbing in the value for the TE of the marble found in (a).

User Balbino
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1 Answer

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Given:

The potential energy of the marble when it is held in the air, PE=0.2 J

The mass of the marble, m=20 g

The initial kinetic energy of the marble, KE=0 J

To find:

(a) The total energy of the marble.

(b) The total energy of the marble before it hits the ground.

Step-by-step explanation:

(a)

The total mechanical energy of an object is the sum of its potential and kinetic energy.

Thus the total energy of the marble when it is dropped is


\begin{gathered} TE=PE+KE \\ =0.2+0 \\ =0.2\text{ J} \end{gathered}

(b)

The total energy of an object will always remains the same as stated by the law of conservation of energy.

Thus the total energy of the marble will be the same as it energy when it was dropped.

Therefore, the total energy of the marble right before it hits the ground is \


TE=0.2\text{ J}

Final answer:

a) The total energy of the marble when it is dropped is 0.2 J

b) The total energy of the marble right before it hits the ground is 0.2 J

User Rajan Mandanka
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