Physics help plz

[hotcommodity]

Question:

 

An interior staircase has steps with a rise(height of step) of 18.5cm and a run(depth of step) of 21.9cm. The height of the staircase is 4.07m. It is desired to make the run of a new staircase 27.4cm. How much farther into the room will the new staircase go? (Answer to be in meters).

 

I don't really get what they're asking for, I guess I just need help setting up the problem...

[timo]

What is the horizontal extent of the old staircase? Try to answer that (maybe draw a diagram). Then, the answer to the question should become easy. "Farther into the room" supposedly means the difference between the old horizontal extent and the new one (in case that was your problem).

[hotcommodity]

Okay, i got 602.8 cm for the length of the new staircase and 481.8cm for the length of the old. Taking the difference of the two and converting that into meters I got 1.21 m, so I guess i'll find out later if its right. Thanks for the reply.

 

edit: 1.21 m is wrong, ahhh!

[timo]

The way I understood the question your answer should be correct, so sorry if I misunderstood the question and led you on the wrong track. Are you sure that 1.21 meters is wrong?

[hotcommodity]

The way I understood the question your answer should be correct, so sorry if I misunderstood the question and led you on the wrong track. Are you sure that 1.21 meters is wrong?

 

It makes sense to me. For our class, we have to enter our answers online, and it tells us if the answer is wrong or not, it came up wrong, but I don't know how else to do it...

[timo]

Can you perhaps post the original wording of the questions in case it wasn´t the same as in your first post?

[hotcommodity]

Sure, here:

 

5. An interior staircase has steps with a rise (height of a step) of 18.5 cm and a run (depth of a step) of 21.9 cm. The of height of the staircase is 4.07 m. It is desired to make the run of a new staircase 27.4 cm. How much farther into the room will the new staircase go?

[timo]

Ok, that is exactly what you posted in your first post. I have no idea of why the 1.21 meters should be wrong, so unless someone else in here has a good idea, you´ll probably have to ask your teacher.

[hotcommodity]

I typed it in a second time just to be sure, and it still comes up as wrong. But thanks for trying

[insane_alien]

try 121 cm the measurements are made in centimetres so give the answer in centimetres.

[timo]

The 1.21 meters is wrong. Hotcommodity already sent me a PM with the correct result (or was it only the calculation and not the result? dunno) but I am not sure if I am supposed to tell it so I´ll leave it to him. Let´s say we were beaten by a quantization effect .

[swansont]

What you need to ask is how many steps are in the staircase. The math used may not be telling you what you think it is. 1.21m is a step too far, as it were.

[hotcommodity]

Well, the problem implied that there were 22 steps, but since the 22nd run would be considered a part of the floor at the top of the staircase, it would not be counted. So what you really have are 22 rises, and 21 runs. Once you know that, it's just a matter of multiplying the 21 runs by their respective lengths, and finally converting the answer to meters.

[mr d]

Hello

 

I thought that should be only 20 risers. The first would be 18.5 cm above the floor, the last 18.5 cm below the upper landing. meaning duction of 37 cm from height.

 

Probably thinking stairway construction.

 

Mr D

[swansont]

Hello

 

I thought that should be only 20 risers. The first would be 18.5 cm above the floor' date=' the last 18.5 cm below the upper landing. meaning duction of 37 cm from height.

 

Probably thinking stairway construction.

 

Mr D[/quote']

 

But that means a height of 21 x .185 m = 3.885 m, which does not jibe with the stated problem.

[mr d]

Hello

 

 

If twenty Risers, 18.5cm to first, 18.5 from last to landing would be plus 37cm needed to be added.

 

or

 

37cm + (18.5cm * 20) = or 37cm + 370cm = 470cm or 4.7 m

 

Again considering construction of say a stircase where a floor and landing are taken into calculations.

 

For the number of Risers to equal 21, the landing would have to be included as a Riser.

or that the height of the last riser needs to be equal to the final height of 4.07m.

 

 

Mr D