--- title: Relative velocity and closing speed | daily.dev description: Closing speed is the normal component of the relative velocity between two objects — the rate at which their distance is changing. Given two objects with... canonical: https://daily.dev/posts/relative-velocity-and-closing-speed-i2bbie8jn twitter:card: summary_large_image twitter:site: @dailydotdev og:type: website og:site_name: daily.dev og:title: Relative velocity and closing speed | daily.dev og:description: Closing speed is the normal component of the relative velocity between two objects — the rate at which their distance is changing. Given two objects with... og:url: https://daily.dev/posts/relative-velocity-and-closing-speed-i2bbie8jn og:image: https://api.daily.dev/og/posts/I2BbIE8Jn.png og:image:alt: Relative velocity and closing speed og:image:width: 1200 og:image:height: 630 og:locale: en --- > ## Documentation Index > Fetch the complete documentation index at: https://daily.dev/llms.txt > Use this file to discover all available pages before exploring further. # Relative velocity and closing speed **[Eli Bendersky](https://daily.dev/sources/elibendersky)** · 5 min read · 1 upvotes · 0 comments ## Summary Closing speed is the normal component of the relative velocity between two objects — the rate at which their distance is changing. Given two objects with position and velocity vectors, the closing speed is computed by projecting the relative velocity onto the unit vector of the line connecting them (using a dot product). A negative result means the objects are approaching; positive means they are separating. The post walks through four concrete examples to build intuition, then extends the concept to a time-dependent formulation using calculus, showing that the instantaneous closing speed equals the time derivative of the scalar distance between the objects. ## Full article daily.dev links to this article rather than hosting it. Read it at the original source: ## Similar posts on daily.dev - [The Geometry Behind the Dot Product: Unit Vectors, Projections, and Intuition](https://daily.dev/posts/the-geometry-behind-the-dot-product-unit-vectors-projections-and-intuition-3humsmybb) · Towards Data Science · 0 upvotes · 0 comments - [Speed Is Never Just Speed](https://daily.dev/posts/speed-is-never-just-speed-yr9gpnx6c) · Fish Food for Thought · 0 upvotes · 0 comments --- Tags: [#game-development](https://daily.dev/tags/game-development), [#physics](https://daily.dev/tags/physics) [View this post on daily.dev](https://daily.dev/posts/relative-velocity-and-closing-speed-i2bbie8jn) ```json {"@context":"https://schema.org","@graph":[{"@type":"Organization","@id":"https://daily.dev/#organization","name":"daily.dev","url":"https://daily.dev","logo":{"@type":"ImageObject","url":"https://daily.dev/apple-touch-icon.png","width":180,"height":180},"sameAs":["https://twitter.com/dailydotdev","https://github.com/dailydotdev","https://www.linkedin.com/company/daily-dev-ltd"]},{"@type":"WebSite","@id":"https://daily.dev/#website","url":"https://daily.dev","name":"daily.dev","publisher":{"@id":"https://daily.dev/#organization"},"potentialAction":{"@type":"SearchAction","target":{"@type":"EntryPoint","urlTemplate":"https://daily.dev/search?q={search_term_string}"},"query-input":"required name=search_term_string"}}]} {"@context":"https://schema.org","@type":"TechArticle","headline":"Relative velocity and closing speed","url":"https://daily.dev/posts/relative-velocity-and-closing-speed-i2bbie8jn","mainEntityOfPage":{"@type":"WebPage","@id":"https://daily.dev/posts/relative-velocity-and-closing-speed-i2bbie8jn"},"datePublished":"2026-08-04T03:01:33.987Z","dateModified":"2026-08-04T03:01:55.659Z","description":"Closing speed is the normal component of the relative velocity between two objects — the rate at which their distance is changing. 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