Deriving the Maximum Speed Equation for Elevator Motors

  • Thread starter Thread starter heart_of_fire
  • Start date Start date
  • Tags Tags
    Maximum Speed
AI Thread Summary
The maximum speed at which an elevator can be raised is derived from the motor's peak power (P) and the mass of the elevator (m), resulting in the equation P/mg. This relationship is established by recognizing that power is the rate at which work is done, expressed as P = dW/dt. Work is defined as the force applied over a distance, leading to the conclusion that power can be related to velocity. The discussion emphasizes the importance of understanding these fundamental concepts to derive the equation correctly. The derivation ultimately shows how motor power directly influences elevator speed.
heart_of_fire
Messages
1
Reaction score
0
A motor of peak power (p) raises an elevator of mass (m)

a)Show that the maximum speed at which the elevator can be raised is P/mg

I guess my question is how did they get P/mg as as the equation for maximum speed?
 
Physics news on Phys.org
The power of the motor goes towards raising the elevator.

Power is defined as the rate at which work is done. P=\frac{dW}{dt}
Consider the fact that work is defined as dW=\vec F \cdot \vec dx and try to find an expression relating the power and the velocity. The answer in the book should point towards it quite strongly.
 

Thread 'Struggling to understand the concept of this question (ice cube in water optics question)'

TL;DR Summary: I came across this question from a Sri Lankan A-level textbook. Question - An ice cube with a length of 10 cm is immersed in water at 0 °C. An observer observes the ice cube from the water, and it seems to be 7.75 cm long. If the refractive index of water is 4/3, find the height of the ice cube immersed in the water. I could not understand how the apparent height of the ice cube in the water depends on the height of the ice cube immersed in the water. Does anyone have an...
View full post »
Thread 'Variable mass system : water sprayed into a moving container'

Thread 'Variable mass system : water sprayed into a moving container'

Starting with the mass considerations #m(t)# is mass of water #M_{c}# mass of container and #M(t)# mass of total system $$M(t) = M_{C} + m(t)$$ $$\Rightarrow \frac{dM(t)}{dt} = \frac{dm(t)}{dt}$$ $$P_i = Mv + u \, dm$$ $$P_f = (M + dm)(v + dv)$$ $$\Delta P = M \, dv + (v - u) \, dm$$ $$F = \frac{dP}{dt} = M \frac{dv}{dt} + (v - u) \frac{dm}{dt}$$ $$F = u \frac{dm}{dt} = \rho A u^2$$ from conservation of momentum , the cannon recoils with the same force which it applies. $$\quad \frac{dm}{dt}...
View full post »

Similar threads

Pushing a block against the wall of an elevator that is accelerating
Replies
42
Views
2K
Find the power needed to accelerate this elevator downward
Replies
4
Views
1K
Power To Accelerate 1000kg Elevator Cab Upward
Replies
31
Views
3K
Problem with the power of car
Replies
3
Views
866
Conservation of Energy Problem (Power)
Replies
14
Views
3K
Climbing a ladder in an elevator
Replies
12
Views
2K
Maximum speed of car on downhill
Replies
1
Views
2K
Peak torque and power for an elevator motor
Replies
7
Views
2K
A Physics 11 Elevator Work/Power Problem
Replies
3
Views
4K
How do you know when k in Hooke's law is positive or negativ
Replies
2
Views
3K

Hot Threads

Recent Insights

Back
Top