---
title: "A small cart is launched with an initial velocity directed up a long, frictionless ramp. The cart slides up the ramp, momentarily comes to rest at its highest point, and then slides back down the ramp. Two students discuss the kinematics of the cart at the exact instant it is at its highest point. Student 1 claims the cart is not accelerating at this instant because its velocity is zero. Student 2 claims the cart is accelerating at this instant because its velocity is changing. Which student is correct, and what is the proper justification?"
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url: "https://nerd-notes.com/ubq/113929/"
date_modified: "2026-06-22T07:38:29+00:00"
---

# A small cart is launched with an initial velocity directed up a long, frictionless ramp. The cart slides up the ramp, momentarily comes to rest at its highest point, and then slides back down the ramp. Two students discuss the kinematics of the cart at the exact instant it is at its highest point. Student 1 claims the cart is not accelerating at this instant because its velocity is zero. Student 2 claims the cart is accelerating at this instant because its velocity is changing. Which student is correct, and what is the proper justification?

A small cart is launched with an initial velocity directed up a long, frictionless ramp. The cart slides up the ramp, momentarily comes to rest at its highest point, and then slides back down the ramp. Two students discuss the kinematics of the cart at the exact instant it is at its highest point. Student 1 claims the cart is not accelerating at this instant because its velocity is zero. Student 2 claims the cart is accelerating at this instant because its velocity is changing. Which student is correct, and what is the proper justification?

![A physical setup showing a cart on a ramp inclined at an angle. An arrow labeled 'v' points up the ramp from the cart. The ramp is long and smooth. A coordinate axis is shown parallel to the ramp with the positive direction pointing up the ramp.](https://nerd-notes.com/wp-content/uploads/ubq-frq-generated/stem-fig-1-1782113908-2Dc1B3.jpg)

- **A.** Student 1, because the acceleration of an object must be zero if its instantaneous velocity is zero.
- **B.** Student 1, because the cart's position is at a maximum and is not changing at that exact instant.
- **C.** Student 2, because the slope of a velocity-vs-time graph for the cart is constant and non-zero as the velocity crosses the time axis.
- **D.** Student 2, because the cart's displacement from its starting position is at its maximum value.

*The answer key and step-by-step explanation are available to logged-in users at https://nerd-notes.com/ubq/113929/*