Power done by elevator

The velocity used in the formula for power is the average velocity. So in this case it would be 1.75 m/s.
  • #1
mkwok
23
0

Homework Statement



A 750 kg elevator starts from rest. It moves upward for 3.00 s with constant acceleration until it reaches its cruising speed, 1.75 m/s.
(a) What is the average power of the elevator motor during this period?(b) How does this power compare with the motor power when the elevator moves at its cruising speed?
Pcruising =

Homework Equations


W=Fd

The Attempt at a Solution



(a)
[tex]\sum[/tex]F = T-mg=ma
Vavg=1.75/2 == > a=1.75/2/3
=> T- 750(9.8) = (750)(1.75/2/3)
T=7568.75N

W=T*d
d=Vavg*t=1.75/2*3
W=7568.75*1.75/2*3=19867.97Am I doing this correctly?

(b) how do I do part b?I don't think I did part a correctly because I got a much different value... and the internet assignment said I am very close
 
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  • #2
mkwok said:

Homework Statement



A 750 kg elevator starts from rest. It moves upward for 3.00 s with constant acceleration until it reaches its cruising speed, 1.75 m/s.
(a) What is the average power of the elevator motor during this period?


(b) How does this power compare with the motor power when the elevator moves at its cruising speed?
Pcruising =


Homework Equations


W=Fd



The Attempt at a Solution



(a)
[tex]\sum[/tex]F = T-mg=ma
Vavg=1.75/2 == > a=1.75/2/3
=> T- 750(9.8) = (750)(1.75/2/3)
T=7568.75N

W=T*d
d=Vavg*t=1.75/2*3
W=7568.75*1.75/2*3=19867.97


Am I doing this correctly?

(b) how do I do part b?


I don't think I did part a correctly because I got a much different value... and the internet assignment said I am very close
Part a you calculated the work correctly. But the question asks for the average power, not the work done. You must note the formula for power as a function of work and time.
For part b, it is simplest to use the formula P=Fv, waht is F in this case??
 
  • #3
I guess F is just the tension? therefore
F = 7568.75N
will v be the final velocity or the average velocity?
 
  • #4
mkwok said:
I guess F is just the tension? therefore
F = 7568.75N
will v be the final velocity or the average velocity?
F is the tension, but since the elevator is cruising at constant speed, and not accelerating, the F will not be 7568N. What is F at constant velocity?
 

What is the definition of power done by an elevator?

The power done by an elevator is the rate at which work is done by the elevator, or the amount of energy transferred per unit of time. It is typically measured in watts (W).

How is the power done by an elevator calculated?

The power done by an elevator can be calculated by multiplying the force exerted by the elevator (measured in newtons) by the velocity at which the elevator is moving (measured in meters per second).

What factors affect the power done by an elevator?

The power done by an elevator can be affected by several factors, including the weight of the elevator and its contents, the height the elevator is traveling, and the speed at which it is moving.

Why is it important to consider the power done by an elevator?

Understanding the power done by an elevator is important in order to ensure that the elevator is functioning efficiently and safely. It can also help in determining the amount of energy needed to power the elevator.

Can the power done by an elevator be increased?

Yes, the power done by an elevator can be increased by increasing the speed at which it travels or by decreasing the weight it is carrying. However, this should only be done within safe limits and according to manufacturer's guidelines.

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