Explain a Moving Cart with Balanced Forces

Supplied materials

• Use the supplied fictional observations or model. Paper and pencil are optional; spoken answers are welcome. No equipment or real experiment is needed.

Learn the idea

The seed model began with a cart at rest. A cart can also begin already moving. When its total horizontal force is zero, its horizontal velocity does not change in our model. It keeps the same speed and direction if already moving, or stays at rest if it started at rest. Balanced forces alone do not tell you its starting motion.

Two paper carts each have 4 units right and 4 units left, with no other horizontal forces. Cart M starts at rest. Cart N starts rolling right at a steady speed. We use a simplified smooth-track model; the listed forces are the entire horizontal total. M stays at rest and N continues steadily right while those conditions hold.

1. Draw equal opposite arrows on M and N.
2. Label M “starts at rest” and N “starts moving right.”
3. Write “zero horizontal net force” beside both.
4. Describe each cart’s unchanged motion separately.

Check your reasoning

Your answer is temporary and is not saved to an account. Download your current answer before leaving or reloading. Written work on paper or in another app stays in your own file.

Take it further

Change N’s starting motion to left at a steady speed, keeping the forces balanced. N continues left at that same speed in the model.

Nothing here is saved to an account or sent to a teacher. The answer download includes your current choice and any checked feedback.