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gizmo_the_mogwai [7]
2 years ago
15

A brick of mass 2 kg is dropped from a rest position 5 m above the ground. what is its velocity at a height of 3 m above the gro

und?
Physics
1 answer:
Rina8888 [55]2 years ago
8 0
We can solve the problem by using the law of conservation of energy.

Using the ground as reference point, the mechanical energy of the brick when it is at 5 m from the ground is just potential energy (because the brick is initially at rest, so it doesn't have kinetic energy):
E= U = mgh=(2 kg)((9.81 m/s^2)(5 m)=98.1 J

when the brick is at h'=3 m from the ground, its mechanical energy is now sum of kinetic energy and potential energy:
E= K+U= \frac{1}{2} mv^2 + mgh'

where v is the velocity of the brick. Since E is conserved, it must be equal to the initial energy (98.1 J), so we can solve this equation to find v:
v= \sqrt{ \frac{2(E-mgh')}{m} }=6.3 m/s
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