Question

If I have just the horsepower and height of an incline, can I get the time?

Answer 1

Yes. Power is defined as:\[P=\frac{ E }{ t }\]where P is power; E is energy; and t is time. So you might be wondering, "From where do I get the energy?"Well, remember that potential energy is energy due to position, and it is defined as:\[E=PE=mgh\]

Answer 2

And if I want to convert the horsepower to m/s, I can do that, correct?

Answer 3

Ok, horsepower is different than velocity (m/s). Do you have anything else other than horsepower, height, and time?

Answer 4

Nope.. But can't you convert horsepower to m/s? Cause you can convert horsepower to ft/min, and then you can convert that to m/s?

Answer 5

1 hp=550 ft-lbf/s=745.7 kg-m^2/s^3.

For some reason I assumed in the beginning you had a mass. I apologize for that. You really need a mass because that mass drives the time over which the power has to be applied.

For instance if I raise 1 kg 10m with a power output of 9.8W, the time needed is calculated as follows:\[t=\frac{ E }{ P }=\frac{ mgh }{ P }=\frac{ 1kg*9.8m/s ^{2}*10m }{ 9.8W}=10\sec\]However if I raise 10kg 10m with a power out put of 9.8W, the time required is:\[t=\frac{ mgh }{ P }=\frac{ 10kg*9.8m/s ^{2}*10m }{ 9.8W }=100s\]So you can see that just having power and height doesn't allow you to calculate time.

Using only power and height, the best you can do is get a "mass velocity": x kg/s.

Answer 6

It may help if you write out the question you have been set in exactly the words you have been given.

You stated that you can conert HP to f/s - but that is not correct.

You can only 'convert' units that have the same dimensions

Power = rate of doing work = F*D/t or F*V
Speed = rate of change of distance = D/T

As Psisquared says 1 HP = 550 ft*lbf/s.

Please let us see the FULL question - more information is needed to solve this question..

Answer 7

@PsiSquared No no, I do have a mass! @MrNood , there is not a specific question in words, but here are the variables that are given.

Answer 8

Maximum power of lift motor: 250 hp
Mass of fully loaded car: 5500 kg
Incline:
or simply 80m straight.

Answer 9

If you have a mass then, like PsiSquared said you can calculate time.

Answer 10

Can you post your question in it's original form, can't get to understand your drawing...

Answer 11

It's not really a written question; let me explain it to you..
I am making a roller coaster (for a project) and it begins with a drop. Because it does this, I made a lift to carry riders from the ground to the entrance (which is located at the top of hill, seeing that the roller coaster starts with a drop). I need to calculate the time for the lift from the ground to the top.

Answer 12

I am given only the variables of the hp, the mass, and that drawing.

Answer 13

okay, so you need to know the workdone in moving up the incline \[W=mgdcos \theta\]

Answer 14

d = 89.89m , find theta using your trig. functions; and \[Power = \frac{Workdone }{ time } = \frac{ mgdcos \theta}{ t}\]

Answer 15

Solve for t.

Answer 16

And the power I would just use the.... horsepower????

Answer 17

@MrNood I think you would only use the mass given for the car..

Answer 18

Nope, convert first to watts

Answer 19

1 hp(I) = 745.699872 W, correct? So I would just multiply my 250hp by 745.7

Answer 20

Also, for the distance.. Would I be using the 80m or the 89m?

Answer 21

yeah @dixiemitsy

Answer 22

Mass of fully loaded car: 5500 kg

It says 'fully loaded'
You are raining a mass of 550kg 80m with 250 HP

Convert all to sensible units and the time will easily drop out of the equations