Answer:
118 N
Explanation:
Given mass of the block, m = 4.00kg.
The acceleration of the elevator, a = 3.0 m/s^2.
As elevotar attaced with spring scale and accelerating upward
(block and elevator), so total force
Here, mg is the weight of the block downward direction.
or
substitute the given value, we get
= 117.6 N = 118 N.
Thus, the reading on the spring scale to 3 significant figures is 118 N.
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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