Day 76: Energy and Momentum Practicum
We did this today in AP Physics C.
The scenario: A cart with a pre-compressed spring travels towards a stationary cart. Upon impact, the spring uncompress and the two carts move away from each other.
The known quantities: The masses of the carts. The pre- and post-impact velocities of just the spring loaded cart as determined by the motion detector.
The challenge: Determine the energy stored in the spring.
The check: Measure the velocity of the spring cart when the spring is used to launch the cart from rest.
(Variation: Given the the compression of the spring, determine the spring constant of the launcher. Check by compressing the launcher with a push/pull spring scale.)
Students must use both momentum and energy conservation to correctly solve this challenge.
CREDIT: Based upon an idea from John Clement’s recent post to the Modeling listserv, in which he envisions a collision which ADDS kinetic energy to the system.