Video Transcript
An object with a mass of 15
kilograms is at a point 10 meters above the ground. What is the gravitational potential
energy of the object?
All right, so let’s say that this
is ground level. And we’re told that our object is
above this level a distance of 10 meters. Along with this, we’re told that
the mass of our object — what we can call 𝑚 — is equal to 15 kilograms. We want to know, what is the
gravitational potential energy of this object? To figure this out, we can recall
that the gravitational potential energy of an object — we can refer to it as GPE —
is equal to the mass of that object multiplied by the strength of the gravitational
field the object is in all times the height of the object above some minimum
possible level. For an object, like the one we have
here, that’s within 10 meters of Earth’s surface, we can say that 𝑔, the
acceleration due to gravity, is exactly 9.8 meters per second squared.
So, when we go to calculate this
object’s gravitational potential energy, we know its mass, that’s 15 kilograms. We know 𝑔, that’s a constant, 9.8
meters per second squared. And we also are given ℎ, the height
of the object above ground level, 10 meters. When we substitute in these values
and then multiply them together, we find a result of 1470 newton meters. This is because a newton is equal
to a kilogram meter per second squared. And then, we can recall further
that a newton times a meter is equal to the unit called a joule. This is the unit typically used to
express energies. So, our final answer is 1470
joules.
