Chair-lift at constant speed: confusion over passengers per minute, power, etc.

In summary, the problem deals with a chair-lift that runs at constant speed and raises 30 passengers per minute, each with an average mass of 75 kg, from the lower station to the upper station with a height difference of 300 metres. The goal is to calculate the power produced by the lift's motors. This can be done by considering the kinetic and potential energy given to each passenger and converting the energy per minute to energy per second, which will give the power produced by the motors.
  • #1
furor celtica
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Homework Statement



A chair-lift runs at constant speed. Each passenger starts from rest at the lower station, and is delivered to the upper station with the speed of the lift. The lift raises 30 passengers a minute, of average mass 75 kg. The top of the lift is 300 metres higher than the bottom, and the ride takes three minutes. What power do the motors produce?

Homework Equations





The Attempt at a Solution



Firstly this exercise confuses me as it is in the middle of (objectively) much simpler problems such as 'a cyclist maintains a steady speed of x ms^1 when opposed by a force of y Newtons, what power is he producing?'; so I'm guessing there is some generalisation or simplification I'm supposed to make, but I'm just missing it.
I'm not even sure of how to formulate the function of the chair-lift exactly, as in the '30 passengers per minute' and the 'ride takes 3 minutes'.

I just need any suggestion of how to tackle this problem, I'm not looking for a full answer or even an overly-detailed explanation.
 
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  • #2
furor celtica said:

Homework Statement



A chair-lift runs at constant speed. Each passenger starts from rest at the lower station, and is delivered to the upper station with the speed of the lift. The lift raises 30 passengers a minute, of average mass 75 kg. The top of the lift is 300 metres higher than the bottom, and the ride takes three minutes. What power do the motors produce?

Homework Equations





The Attempt at a Solution



Firstly this exercise confuses me as it is in the middle of (objectively) much simpler problems such as 'a cyclist maintains a steady speed of x ms^1 when opposed by a force of y Newtons, what power is he producing?'; so I'm guessing there is some generalisation or simplification I'm supposed to make, but I'm just missing it.
I'm not even sure of how to formulate the function of the chair-lift exactly, as in the '30 passengers per minute' and the 'ride takes 3 minutes'.

I just need any suggestion of how to tackle this problem, I'm not looking for a full answer or even an overly-detailed explanation.

When people leave a chairlift, they have the speed of the chair lift, so if they started at rest they will have been given a little kinetic energy [0.5 m v2] by the lift. There is enough information given to calculate what the speed is.

Each rider is also raised up quite a distance, so there will be quite a gain in potential energy [mgh].

Now that total amount of energy is given to each passenger, an a lot of them are carried up each minute.

It is quite straight forward to change "Joules per minutes" to "joules per second" and that will be Power!
 
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1. How is the power of a chair-lift at constant speed calculated?

The power of a chair-lift at constant speed is calculated by multiplying the force required to lift the passengers by the speed at which the lift is moving. This can be represented by the formula Power = Force x Speed.

2. What is the relationship between the number of passengers per minute and the power of a chair-lift at constant speed?

The number of passengers per minute does not directly affect the power of a chair-lift at constant speed. However, the weight of the passengers does play a role in determining the power, as it affects the force required to lift them.

3. Why do some people get confused about the concept of passengers per minute when discussing the power of a chair-lift at constant speed?

Some people may get confused because they assume that the number of passengers per minute is directly related to the power of the chair-lift. However, as mentioned earlier, the weight of the passengers is a more significant factor in determining the power.

4. Is the power of a chair-lift at constant speed constant?

Yes, the power of a chair-lift at constant speed remains constant as long as the force required to lift the passengers and the speed of the lift remain the same. This means that the power will not change even if the number of passengers per minute varies.

5. How does the power of a chair-lift at constant speed compare to other types of lifts?

The power of a chair-lift at constant speed may be lower than other types of lifts, such as a gondola or a high-speed detachable lift. This is because these lifts may require more power to overcome friction and move at higher speeds. However, the power of a chair-lift may be higher than a surface lift, such as a T-bar or rope tow, due to the added weight of the chairs or gondolas.

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