# Force and Motion: Creating Two Classic Physics Questions in Real Life

7 min readJul 16, 2024

There are two questions that can really give some insight into complicated physics concepts. However, I want to do more than just ask the questions. I want to SHOW these situations using the Vernier Fan Carts.

OK, let me start off with the easier of the two questions.

# Same Force for the Same Time

Imagine I have two carts on frictionless tracks. Cart A has a mass of m and cart B has a mass of 2m (twice the mass). The two carts each have a fan that pushes with a constant force (the carts have the same force) and are released from rest. If the forces act for 3 seconds, consider the following.

• How do the final speeds of cart A and B compare?
• How do the final momentums (in the x-direction) for A and B compare?
• How do the final kinetic energies for A and B compare?

Justify your answer.

Now I’m going to tell you the answer (and then we can actually do it).

If cart B has twice the mass, with the same force it will have half the acceleration. This…

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Physics faculty, science blogger of all things geek. Technical Consultant for CBS MacGyver and MythBusters. WIRED blogger.