A car travels at 60mph, a truck travels 55mph in the opposite direction. The vehicles pass in .34 seconds. How long is the truck?

How do I set this problem up??

Results 1 to 9 of 9

- October 18th 2012, 09:41 AM #1

- October 18th 2012, 11:19 AM #2

- October 18th 2012, 01:48 PM #3

- October 18th 2012, 03:36 PM #4

- October 19th 2012, 02:09 AM #5

- Joined
- Oct 2009
- Posts
- 5,513
- Thanks
- 769

## Re: How do I set up this problem?

The solutions above assume that the time it takes for the vehicles to pass is measured from the moment when their front bumpers align to the moment when the front bumper of the car aligns with the back of the truck. During this time, the car travels the whole truck's length relative to the truck. This is why the rate of closure times 0.34 s presumable equals the length of the truck. However, at the end of this time, the car and the truck still overlap. If we measure the passing time as the time when the vehicles overlap, then the rate of closure times 0.34 s equals the combined lengths of the vehicles.

- October 19th 2012, 06:39 AM #6

- Joined
- May 2006
- From
- Lexington, MA (USA)
- Posts
- 11,682
- Thanks
- 614

## Re: How do I set up this problem?

Hello, Ranger SVO!

A car travels at 60mph, a truck travels 55mph in the opposite direction.

The vehicles pass in 0.34 seconds. .How long is the truck?

Is that a misprint?

If this is conventional "passing vehicles", there is no unique solution.

. . We would need the length of the car.

Normally, the passing procedure begins when their front bumpers are even

. . and ends when their*rear bumpers are even.*

Code:* - - * | car | → * - - * Start * - - - - * ← | truck | * - - - - * * - - * | car | → End * - - * * - - - - * ← | truck | * - - - - *

Let = length of the truck.

They have a combined speed of mph.

It is as if the car has*stopped*

. . and the truck is passing at 115 mph.

The truck travels feet at ft/sec

. . and takes 0.34 seconds.

We have: . feet.

The combined lengths of both vehicles is*less than a half-inch!*

And we still don't know the value of

- October 19th 2012, 07:06 AM #7

- Joined
- Oct 2009
- Posts
- 5,513
- Thanks
- 769

- October 19th 2012, 04:04 PM #8

- October 21st 2012, 08:19 AM #9

- Joined
- Nov 2007
- From
- Trumbull Ct
- Posts
- 904
- Thanks
- 27