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Question Video: Gravitational Potential Energy Physics • 9th Grade

An object with a mass of 15 kg is at a point 10 m above the ground. What is the gravitational potential energy of the object?

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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.

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