Â鶹´«Ã½

A cyclist saves energy by staying in the slipstream of the rider in front. But does the rider in front expend more energy than a solo rider travelling at the same speed?

Paul Fairfield,

Bebington, Merseyside, UK

If Earth stopped rotating, would this affect the force of gravity?

Lyn Williams,

Neath, Port Talbot, UK

To answer this question – or ask a new one – email lastword@newscientist.com.

Questions should be scientific enquiries about everyday phenomena, and both questions and answers should be concise. We reserve the right to edit items for clarity and style. Please include a postal address, daytime telephone number and email address.

Â鶹´«Ã½ retains total editorial control over the published content and reserves all rights to reuse question and answer material that has been submitted by readers in any medium or in any format.

Terms and conditions apply.