Physics help please

[bens250ex]

Need a little help guys. here is the problem if you are bored and know what to do please help me out. also if you do please tell me how you did it :D

If a 1000lb elevator has a 10 Hp motor, how long would it take to pull the elevator up 100ft? (assuming 100% efficient and no stops)


i know its suppose to be easy stuff but teacher failed to show us.

[juice420]

Them theres school words, I's not so good with schoolin'.:huh

[slightlybent47]

That’s easy…….. The question never said that a 10 hp motor will even lift a 1000 lbs elevator.

[dustin_j]

Convert everything to metric and use units to show you how to do it. Remember: kW = hp * .7457; W = J/s = Nm/s = kg m^2 / s^2

[PhilMoore]

Originally posted by bens250ex
Need a little help guys. here is the problem if you are bored and know what to do please help me out. also if you do please tell me how you did it :D

If a 1000lb elevator has a 10 Hp motor, how long would it take to pull the elevator up 100ft? (assuming 100% efficient and no stops)


i know its suppose to be easy stuff but teacher failed to show us.



Your Idea sounds like something BP would come up with...'



BTW, the answer to your question is "TOO D^m LONG"

[steel1]

dont u need to know the gear ratio. a ten horse motor isnt enough to lift 1000lbs. it would need a gear box for reduction

[dustin_j]

It's a theoretical question, so the gearbox doesn't matter if it's 100% efficient. You need to determine the amount of Work needed to lift the elevator 100ft. Work = Force * Displacement, or mass * gravity * height. This is why metric units are nice, because kg*(m/s^2)*m = N*m = Joules.

So you know the amount of work you need to do. Convert your motor hp to Watts (joules/second). Work / power (J / (J/s)), gives you the time required to do the work. The answer is ~18 seconds. You can do this in standard units, but the conversions along the way aren't as straightforward.

PhilMoore, were you referring to my idea as something BP would do? Because I doubt the "English" would use the "metric" system, haha.

[steel1]

Originally posted by dustin_j
It's a theoretical question, so the gearbox doesn't matter if it's 100% efficient. You need to determine the amount of Work needed to lift the elevator 100ft. Work = Force * Displacement, or mass * gravity * height. This is why metric units are nice, because kg*(m/s^2)*m = N*m = Joules.

So you know the amount of work you need to do. Convert your motor hp to Watts (joules/second). Work / power (J / (J/s)), gives you the time required to do the work. The answer is ~18 seconds. You can do this in standard units, but the conversions along the way aren't as straightforward.

PhilMoore, were you referring to my idea as something BP would do? Because I doubt the "English" would use the "metric" system, haha.
I thought Americans hated the metric system........just because. Conversions are the worst. Waste of time.

[dustin_j]

Originally posted by steel1
I thought Americans hated the metric system........just because. Conversions are the worst. Waste of time.

I think Americans hate the metric system because it's different. Conversions in metric use multiples of 10 (mostly); where, standard uses 12, 4, 16...not to mention fractions, etc. Metric is just hard to quantify if you grew up using standard/english.

[dehner47]

Originally posted by dustin_j
I think Americans hate the metric system because it's different. Conversions in metric use multiples of 10 (mostly); where, standard uses 12, 4, 16...not to mention fractions, etc. Metric is just hard to quantify if you grew up using standard/english.

your pretty smart when it comes to the math and the equation stuff. are you a math student or math teacher, engineer or something??

[dustin_j]

Originally posted by dehner47
your pretty smart when it comes to the math and the equation stuff. are you a math student or math teacher, engineer or something??

engineer, graduated last may