Question

Please explain simply! I've done this many times, but I still do not understand.

A man is walking at an average speed of 4 miles per hour alongside a railroad track. A freight train, going in the same direction at an average speed of 30 miles per hour, requires 5 seconds to pass the man. How long is the freight train. Give your answer in feet.

Answer 1

I would ask this first, how long is the man?

Answer 2

( I mean b/f solving your...have to know how long is the man)

Answer 3

The relative speed of the freight train with respect to the man is: 30 mph - 4 mph = 26 mph.
So How much will the train move in 5 seconds when travelling at 26 mph?

Answer 4

what do you mean by how long is the man

Answer 5

why would you subtract 4 from 30?

Answer 6

I mean if the train passes the man, doesn't the man have to be certain length (normally referred to as fat) if the man is 4 feet wide it would take .3 seconds longer or something....

Answer 7

To find out how much faster does the train travel from the man.

Answer 8

It is called relative speed.
Two objects are moving simultaneously in the same direction.
So bring the man to a standstill by applying a 4 mph speed to the man. Then you should do the same for the train too. So now the man is absolutely still and the train is moving relative to him at 26 mph.

Answer 9

oh, i knew i had to do something like that. but i didnt know how

Answer 10

so you know how to solve it now?

Answer 11

yes, thank you. i got the answer and i understand how to do it now

Answer 12

Good!