Question Video: Determining the Gravitational Potential Energy of a Mass Physics • First Year of Secondary School

Video Transcript

An apple that hangs from a tree branch 4.5 meters above ground has a weight of 1.2 newtons. What is the apple’s gravitational potential energy?

Let’s say that this here is our apple. It’s hanging a height we’ll call ℎ of 4.5 meters above ground level. Along with this, we’re told that the weight of the apple, we’ll call it 𝑊, is 1.2 newtons. Knowing all this, we want to solve for the apple’s gravitational potential energy 𝐸. In general, an object’s gravitational potential energy equals its mass times the acceleration due to gravity multiplied by that object’s height above some reference level.

In order to use this equation, let’s also recall that an object’s weight in a gravitational field equals the object’s mass times the acceleration due to gravity. This means we can combine these two equations and get 𝐸 equals 𝑊 times ℎ. For our apple, we know both of those values. 𝑊 is 1.2 newtons and ℎ is 4.5 meters. The product of these two values comes out to 5.4 joules. That’s the gravitational potential energy of our apple at the given height.