Speed

The math is quite correct. What you're missing is that truck is capable of generating speeds of 400 mph but it doesn't achieve that speed in just 6.5 seconds. Due to its drag and inertia, the jet truck takes a little more time to its greatest speed and max out on its power curve. Take a look at the speed of the truck after about 20 seconds and it'll be a lot closer to 400 mph. That's even more impressive.

However when you compare what times most faster (non-supercharged or turbo) racing vehicles to reach 1/4 mile (about 90-95 mph) speed (taking far longer than 6.5 seconds to do it), that truck's traveling mighty fast.

As a comparison, a supercharged Corvette just ran the 1/4 mile in 11.84 sec @ 117 mph. FWIW, this Vette's max speed is only 163 mph vs. the truck's max speed which is at 400 mph.

Thank you Ragman.

If you want average speed, that is correct. If you want top speed, assuming constant acceleration, then it's double that.

Where does it say that in the question? In fact the question just says that the truck "covers" a quarter mile in 6.5 seconds, and requires the "speed". I cannot see anything which says that it's a standing quarter mile. Also, all that "world's fastest jet truck" stuff is just modern school type dressing up of the problem. It could just as easily have been my 1978 Laverda Jota motorcycle. Or "a moving vehicle". Like instead of saying "divide 65 by 5" these days you have to say "Jane has 65 doggy choc drops and wants to share them between 5 little puppy dogs".

Thanks markr.

contrex,

Here is a link to the article about the truck:
http://www.dailymail.co.uk/news/article-2561173/One-lorry-wont-stuck-Introducing-400mph-Shockwave-worlds-fastest-truck-outrun-Japanese-bullet-train.html

Thanks.

Randy Dandy

It says that in the link to the vehicle he was writing about. I Googled it.

Where does it say, in the original question as asked, that the quarter mile was from a standing start? Here it is again: "The world's fastest jet truck covers a quarter mile in 6.5 seconds. Calculate speed of the truck."