Complete Question
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Answer:
The velocity is
Explanation:
The kinetic energy of the 9 kg can be determined by these expression
Kinetic energy of 9 kg block = initial energy stored - energy lost as a result of friction
Now to obtain the initial energy stored
Let U denote the initial energy stored and

Where x is the length the spring is displaced
k is the force constant of the string


Now referring to the formula above
i.e Kinetic energy of 9 kg block = initial energy stored - energy lost as a result of friction



and we are told that coefficient of friction = 0.4 and the mass is 9 kg ,the acceleration due to gravity
this displacement length of spring = 0.6
Therefore 
Because the action and the reaction forces act on different objects
Explanation:
Newton's third law of motion states that:
<em>"When an object A exerts a force on an object B (action), then object B exerts an equal and opposite force (reaction) on object A"</em>
From the statement above, we clearly see that the two forces mentioned in the law act on different objects. In fact, the action is exerted on object B, while the reaction is exerted on object A.
When we are considering the free-body diagram of an object, we just represent all the forces acting on that object, but not the forces exerted on other objects: this means that the action and the reaction never appear in the same free-body diagram of the same object, so they do not cancel out, simply because they are applied to different objects.
Learn more about Newton's third law:
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Answer:mostly likely from volcanos
Explanation:
when the volcano erupts the magma becomes lava and cools making igneous rocks
The stereo uses an energy of

in a time

, therefore the power of the stereo is given by

We also know that the power of an electrical device is related to its voltage, V, and its resistance, R, by the following equation

therefore, we can rearrange the equation to calculate the resistance of the stereo: