What is the correct explanation of Newton's Third Law of Motion?
2 answers:
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The potential energy of the rock is 30,000 J
Explanation:
The mechanical energy of an object is equal to the sum of its gravitational potential energy (PE) and its kinetic energy (KE):
where
PE is the gravitational potential energy, which is the energy possessed by the object due to its position in the gravitational field
KE is the kinetic energy, which is the energy possessed by the object due to its motion
In this problem, the rock is at rest, so its kinetic energy is zero:
KE = 0
Therefore, the energy of the rock is just equal to its potential energy, which is:
where
m = 10.2 kg is the mass of the rock
is the acceleration of gravity
h = 300 m is the height of the rock above the ground
Substituting and solving, we find
Learn more about potential energy:
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Answer:
The speed after being pulled is 2.4123m/s
Explanation:
The work realize by the tension and the friction is equal to the change in the kinetic energy, so:
(1)
Where:
Because the work made by any force is equal to the multiplication of the force, the displacement and the cosine of the angle between them.
Additionally, the kinetic energy is equal to , so if the initial velocity
is equal to zero, the initial kinetic energy
is equal to zero.
Then, replacing the values on the equation and solving for , we get:
So, the speed after being pulled 3.2m is 2.4123 m/s