Name: __________________
Girl on a Trampoline
The objective of this activity is to determine the velocity of the girl as she leaves the trampoline.
We can do this by using the Law of Conservation of Energy.
We know that:
∆𝐸𝑚𝑒𝑐ℎ = 0
∆𝐸𝑚𝑒𝑐ℎ 𝑖 = ∆𝐸𝑚𝑒𝑐ℎ 𝑓
𝐺𝑃𝐸𝑖 + 𝐾𝐸𝑖 = 𝐺𝑃𝐸𝑓 + 𝐾𝐸𝑓
𝑚𝑔ℎ𝑖 +
1
1
𝑚𝑣𝑖2 = 𝑚𝑔ℎ𝑓 + 𝑚𝑣𝑓2
2
2
By using the law of conservation of energy we are able to determine an unknown velocity at a
certain point, as long we know her potential energies and a kinetic energy.
1. If the girl has a mass of 120 lbs, what is her mass in kg? Show your work! (1 kg = 2.2 lbs)
Open the video of the girl on the trampoline using QuickTime player. Watch it twice to
familiarize yourself with the video, this will help you know what part of the video you will want
to use for your calculations.
2. What is the equation for gravitational potential energy?
3. What is the girl’s potential energy when she is just about to leave the trampoline in reference to
the ground? Show your work!
To calculate this you need to advance the video frame by frame to determine where the girl is just
about to leave the trampoline. To do this you need to click on the spacebar to play the video and
then use the arrow keys to advance the video frame by frame.
4. What is the girl’s potential energy when she reaches her maximum height above the trampoline
in reference to the ground? (Show your work!)
5. Using these two potential energies, what is her velocity as she leaves the trampoline?